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opendkim.conf(5) - phpMan
opendkim.conf(5) File Formats Manual opendkim.conf(5)
NAME
opendkim.conf - Configuration file for opendkim
LOCATION
/etc/opendkim.conf
DESCRIPTION
opendkim(8) implements the DKIM specification for signing and verifying e-mail messages on
a per-domain basis. This file is its configuration file.
Blank lines are ignored. Lines containing a hash ("#") character are truncated at the
hash character to allow for comments in the file.
Other content should be the name of a parameter, followed by white space, followed by the
value of that parameter, each on a separate line.
For parameters that are Boolean in nature, only the first byte of the value is processed.
For positive values, the following are accepted: "T", "t", "Y", "y", "1". For negative
values, the following are accepted: "F", "f", "N", "n", "0".
Many, but not all, of these parameters are also available as command line options to
opendkim(8). However, new parameters are generally not added as command line options so
the complete set of options is available here, and thus use of the configuration file is
encouraged. In some future release, the set of available command line options is likely
to get trimmed.
See the opendkim(8) man page for details about how and when the configuration file con‐
tents are reloaded.
Some of these parameters are listed as having a type of "dataset". See the opendkim(8)
man page for a description of such parameters.
Unless otherwise stated, Boolean values default to "false", integer values default to 0,
and string and dataset values default to being undefined.
PARAMETERS
AddAllSignatureResults (Boolean)
If "true", results for all signatures will be reported by an added Authentication-
Results header field. Otherwise, only one signature will be reported, and which
one depends on the TrustSignaturesFrom setting or, in its absence, which one(s)
passed first or, if none passed, which one was found first during message process‐
ing.
ADSPAction (string)
Selects the action to be taken when an ADSP check against a message with no valid
author signature results in the message being deemed suspicious and discardable.
Possible values are "discard" (accept the mesasge but throw it away) and "reject"
(bounce the message). If not set, discardable messages will still be delivered.
ADSPNoSuchDomain (Boolean)
If "true", requests rejection of messages that are determined to be from nonexis‐
tent domains according to the author domain signing practises (ADSP) test.
AllowSHA1Only (Boolean)
Permit verify mode when only SHA1 support is available. RFC6376 requires that ver‐
ifiers implement both SHA1 and SHA256 support. Setting this feature changes the
absence of SHA256 support from an error to a warning.
AlwaysAddARHeader (Boolean)
Add an "Authentication-Results:" header field even to unsigned messages from
domains with no "signs all" policy. The reported DKIM result will be "none" in
such cases. Normally unsigned mail from non-strict domains does not cause the
results header field to be added.
AuthservID (string)
Sets the "authserv-id" to use when generating the Authentication-Results: header
field after verifying a message. The default is to use the name of the MTA pro‐
cessing the message. If the string "HOSTNAME" is provided, the name of the host
running the filter (as returned by the gethostname(3) function) will be used.
AuthservIDWithJobID (Boolean)
If "true", requests that the authserv-id portion of the added Authentication-
Results: header fields contain the job ID of the message being evaluated.
AutoRestart (Boolean)
Automatically re-start on failures. Use with caution; if the filter fails
instantly after it starts, this can cause a tight fork(2) loop.
AutoRestartCount (integer)
Sets the maximum automatic restart count. After this number of automatic restarts,
the filter will give up and terminate. A value of 0 implies no limit; this is the
default.
AutoRestartRate (string)
Sets the maximum automatic restart rate. If the filter begins restarting faster
than the rate defined here, it will give up and terminate. This is a string of the
form n/t[u] where n is an integer limiting the count of restarts in the given
interval and t[u] defines the time interval through which the rate is calculated; t
is an integer and u defines the units thus represented ("s" or "S" for seconds, the
default; "m" or "M" for minutes; "h" or "H" for hours; "d" or "D" for days). For
example, a value of "10/1h" limits the restarts to 10 in one hour. There is no
default, meaning restart rate is not limited.
Background (Boolean)
Causes opendkim to fork and exits immediately, leaving the service running in the
background. The default is "true".
BaseDirectory (string)
If set, instructs the filter to change to the specified directory using chdir(2)
before doing anything else. This means any files referenced elsewhere in the con‐
figuration file can be specified relative to this directory. It's also useful for
arranging that any crash dumps will be saved to a specific location.
BodyLengthDB (dataset)
Requests that opendkim include a "l=" body length tag when the set contains any of
the envelope recipient addresses. The addresses presented are tested against the
database in various forms as described under the SigningTable setting (below).
This feature of the protocol exists to improve the likelihood that a signature will
survive transit through a mailing list server, as they commonly append footers to
messages. Note, however, that this creates a potential security issue since some‐
one could add arbitrary text to the signed message and the signature would still
validate. See the DKIM specification for details.
BogusKey (string)
Instructs the filter to treat a passing signature associated with a bogus (forged)
key in a special way. Possible values are neutral (return a "neutral" result),
none (take no special action) and fail (return a "fail" result; this is the
default).
BogusPolicy (string)
Instructs the filter to treat an ADSP policy found in an bogus (forged) DNS record
in a special way. Possible values are apply (apply the policy) and ignore (ignore
the policy; this is the default).
CaptureUnknownErrors (Boolean)
When set, and on systems where MTA quarantine is available, the filter will request
quarantine of a message that results in an internal error or resource exhaustion.
Canonicalization (string)
Selects the canonicalization method(s) to be used when signing messages. When ver‐
ifying, the message's DKIM-Signature: header field specifies the canonicalization
method. The recognized values are relaxed and simple as defined by the DKIM speci‐
fication. The default is simple. The value may include two different canonical‐
izations separated by a slash ("/") character, in which case the first will be
applied to the header and the second to the body.
ChangeRootDirectory (string)
Requests that the operating system change the effective root directory of the
process to the one specified here prior to beginning execution. chroot(2) requires
superuser access. A warning will be generated if UserID is not also set.
ClockDrift (integer)
Sets the tolerance in seconds to be applied when determining whether a signature
was either expired or generated in the future. The default is 300.
Diagnostics (Boolean)
Requests the inclusion of "z=" tags in signatures, which encode the original header
field set for use by verifiers when diagnosing verification failures. Not recom‐
mended for normal operation.
DiagnosticDirectory (string)
Directory into which to write diagnostic reports when message verification fails on
a message bearing a "z=" tag. If not set (the default), these files are not gener‐
ated.
DisableADSP (Boolean)
If set, suppresses Author Domain Signing Practices (ADSP) checks, which require
multiple additional DNS queries.
DisableCryptoInit (Boolean)
If set, skips initialization of the SSL library initialization steps, which are
normaly required in multi-threaded environments. This assumes some other library
opendkim is using will do the required initialization and shutdown.
DNSConnect (Boolean)
Requests that the asynchronous resolver start using TCP immediately rather than
using UDP until TCP is actually needed. Does not work with all resolvers.
DNSTimeout (integer)
Sets the DNS timeout in seconds. A value of 0 causes an infinite wait. The
default is 5. Ignored if not using an asynchronous resolver package. See also the
NOTES section below.
Domain (dataset)
A set of domains whose mail should be signed by this filter. Mail from other
domains will be verified rather than being signed.
This parameter is not required if a SigningTable is in use; in that case, the list
of signed domains is implied by the lines in that file.
This parameter is ignored if a KeyTable is defined.
DomainKeysCompat (boolean)
If set, backward compatibility with DomainKeys (RFC4870) key records is enabled.
When not set, such keys are considered to be syntactically invalid. The default is
"false".
DontSignMailTo (dataset)
A set of e-mail address, mail to which should never be signed by the filter. Note
that this is an "any" feature; if any one of the recipients of the message matches
a member of this list, the message will not be signed.
EnableCoredumps (boolean)
On systems that have such support, make an explicit request to the kernel to dump
cores when the filter crashes for some reason. Some modern UNIX systems suppress
core dumps during crashes for security reasons if the user ID has changed during
the lifetime of the process. Currently only supported on Linux.
ExemptDomains (dataset)
Specifies a set of domains, mail from which should be ignored entirely by the fil‐
ter. This is similar to the PeerList setting except that it bases its decision on
the sender of the message as identified from the header fields or other message
data, not the identity of the SMTP client sending the message.
ExternalIgnoreList (dataset)
Identifies a set of "external" hosts that may send mail through the server as one
of the signing domains without credentials as such. This has the effect of sup‐
pressing the "external host (hostname) tried to send mail as (domain)" log mes‐
sages. Entries in the data set should be of the same form as those of the PeerList
option below. The set is empty by default.
FinalPolicyScript (string)
Gives the name of a Lua script that should be run after the entire message has been
received. This can be used to enact local policy decisions such as message rejec‐
tion, quarantine, rerouting, etc. based on signatures found on the message, the
results of attempts to verify them, and other properties of the message or signa‐
tures. See opendkim-lua(3) for details.
FixCRLF (Boolean)
Requests that the DKIM library convert bare CRs and LFs to CRLFs during body canon‐
icalization, anticipating that an MTA somewhere before delivery will do that con‐
version anyway. The default is to leave them as-is.
IdentityHeader (string)
This specifies the header field where an identity is stored. (Experimental feature
not enabled for this installation.)
IdentityHeaderRemove (Boolean)
Remove the IdentityHeader after signing. (Experimental feature not enabled for
this installation.)
Include (string)
Names a file to be opened and read as an additional configuration file. Nesting is
allowed to a maximum of five levels.
InternalHosts (dataset)
Identifies a set internal hosts whose mail should be signed rather than verified.
Entries in this data set follow the same form as those of the PeerList option
below. If not specified, the default of "127.0.0.1" is applied. Naturally, pro‐
viding a value here overrides the default, so if mail from 127.0.0.1 should be
signed, the list provided here should include that address explicitly.
KeepAuthResults (boolean)
Suppresses removal of Authentication-Results header fields containing DKIM results
apparently added by this filter (usually the result of a misconfiguration or a
forgery).
KeepTemporaryFiles (boolean)
Instructs the filter to create temporary files containing the header and body
canonicalizations of messages that are signed or verified. The location of these
files can be set using the TemporaryDirectory parameter. Intended only for debug‐
ging verification problems.
KeyFile (string)
Gives the location of a PEM-formatted private key to be used for signing all mes‐
sages. Ignored if a KeyTable is defined.
KeyTable (dataset)
Gives the location of a file mapping key names to signing keys. If present, over‐
rides any KeyFile setting in the configuration file. The data set named here maps
each key name to three values: (a) the name of the domain to use in the signature's
"d=" value; (b) the name of the selector to use in the signature's "s=" value; and
(c) either a private key or a path to a file containing a private key. If the
first value consists solely of a percent sign ("%") character, it will be replaced
by the apparent domain of the sender when generating a signature. If the third
value starts with a slash ("/") character, or "./" or "../", then it is presumed to
refer to a file from which the private key should be read, otherwise it is itself a
PEM-encoded private key or a base64-encoded DER private key; a "%" in the third
value in this case will be replaced by the apparent domain name of the sender. The
SigningTable (see below) is used to select records from this table to be used to
add signatures based on the message sender.
LDAPAuthMechanism (string)
Names the authentication mechanism to use when connecting to an LDAP server. The
default is the empty string, meaning "simple" authentication should be done.
LDAPAuthName (string)
Specifies the authenticating name to use when using SASL to authenticate to an LDAP
server. Requires SASL support be installed on the local system. There is no
default.
LDAPAuthRealm (string)
Specifies the authentication realm to use when using SASL to authenticate to an
LDAP server. Requires SASL support be installed on the local system. There is no
default.
LDAPAuthUser (string)
Specifies the authenticating user to use when using SASL to authenticate to an LDAP
server. Requires SASL support be installed on the local system. There is no
default.
LDAPBindPassword (string)
Specifies the password to use when conducting an LDAP "bind" operation. There is
no default.
LDAPBindUser (string)
Specifies the user ID to use when conducting an LDAP "bind" operation. There is no
default.
LDAPDisableCache (Boolean)
Suppresses creation of a local cache in front of LDAP queries.
LDAPKeepaliveIdle (integer)
Sets the number of seconds a connection to an LDAP server needs to remain idle
before TCP starts sending keepalive probes. If not specified, the LDAP library
default is used.
LDAPKeepaliveInterval (integer)
Sets the interval in seconds between TCP keepalive probes. If not specified, the
LDAP library default is used.
LDAPKeepaliveProbes (integer)
Sets the maximum number of keepalive probes TCP should send before abandoning the
connection. If not specified, the LDAP library default is used.
LDAPSoftStart (Boolean)
If set, the inability to bind and authenticate to an LDAP server will not prevent
the filter from starting, and reconnections will be attempted for each query. The
default is "False".
LDAPTimeout (integer)
Sets the time in seconds after which an LDAP operation should be abandoned. The
default is 5.
LDAPUseTLS (Boolean)
Indicates whether or not a TLS connection should be established when contacting an
LDAP server. The default is "False".
LocalADSP (dataset)
Allows specification of local ADSP overrides for domains. This is expected to be a
data set with keys and matching values; the keys are each either a fully-qualified
domain name (e.g. "foo.example.com") or a subdomain name preceded by a period (e.g.
".example.com"), and the values are either unknown, all, or discardable, as per the
ADSP specification (RFC5617). This allows local overrides of policies to enforce
for domains that either don't publish ADSP or publish weaker policies than the ver‐
ifier would like to enforce.
LogResults (boolean)
If logging is enabled (see Syslog below), requests that the results of evaluation
of all signatures that were at least partly intact (i.e., the "d=", "s=", and "b="
tags could be extracted).
LogWhy (boolean)
If logging is enabled (see Syslog below), issues very detailed logging about the
logic behind the filter's decision to either sign a message or verify it. The
logic behind the decision is non-trivial and can be confusing to administrators not
familiar with its operation. A description of how the decision is made can be
found in the OPERATIONS section of the opendkim(8) man page. This causes a large
increase in the amount of log data generated for each message, so it should be lim‐
ited to debugging use and not enabled for general operation.
MacroList (dataset)
Defines a set of MTA-provided macros that should be checked to see if the sender
has been determined to be a local user and therefore whether or not the message
should be signed. If a value is specified matching a macro name in the data set,
the value of the macro must match a value specified (matching is case-sensitive),
otherwise the macro must be defined but may contain any value. The set is empty by
default, meaning macros are not considered when making the sign-verify decision.
The general format of the value is value1[|value2[|...]]; if one or more value is
defined then the macro must be set to one of the listed values, otherwise the macro
must be set but can contain any value.
In order for the macro and its value to be available to the filter for checking,
the MTA must send it during the protocol exchange. This is either accomplished via
manual configuration of the MTA to send the desired macros or, for MTA/filter com‐
binations that support the feature, the filter can request those macros that are of
interest. The latter is a feature negotiated at the time the filter receives a
connection from the MTA and its availability depends upon the version of milter
used to compile the filter and the version of the MTA making the connection.
This data set must be of type "file" or "csl".
MaximumHeaders (integer)
Defines the maximum number of bytes the header block of a message may consume
before the filter will reject the message. This mitigates a denial-of-service
attack in which a client connects to the MTA and begins feeding an unbounded number
of header fields of arbitrary size; since the filter keeps a cache of these, the
attacker could cause the filter to allocate an unspecified amount of memory. The
default is 65536; a value of 0 removes the limit.
MaximumSignaturesToVerify (integer)
Defines the maximum number of signatures on a message for which verification should
be conducted. The default is three. Signatures are selected from the top of the
message downward. If TrustSignaturesFrom is set, signatures from domains in that
data set are always verified, which may consume part or all of, or even exceed,
this limit. Note that this could cause an author domain signature to be ignored,
causing the ADSP evaluation to fail and, if SendADSPReports is enabled, a question‐
able report could be generated.
MaximumSignedBytes (integer)
Specifies the maximum number of bytes of message body to be signed. Messages
shorter than this limit will be signed in their entirety. Setting this value
implies use of BodyLengthDB for all addresses.
MilterDebug (integer)
Sets the debug level to be requested from the milter library. The default is 0.
Minimum (string)
Instructs the verification code to fail messages for which a partial signature was
received. There are three possible formats: min indicating at least min bytes of
the message must be signed (or if the message is smaller than min then all of it
must be signed); min% requiring that at least min percent of the received message
must be signed; and min+ meaning there may be no more than min bytes of unsigned
data appended to the message for it to be considered valid.
MinimumKeyBits (integer)
Establishes a minimum key size for acceptable signatures. Signatures with smaller
key sizes, even if they otherwise pass DKIM validation, will me marked as invalid.
The default is 1024, which accepts all signatures. A value of 0 causes the default
to be used.
Mode (string)
Selects operating modes. The string is a concatenation of characters that indicate
which mode(s) of operation are desired. Valid modes are s (signer) and v (veri‐
fier). The default is sv except in test mode (see the opendkim(8) man page) in
which case the default is v. When signing mode is enabled, one of the following
combinations must also be set: (a) Domain, KeyFile, Selector, no KeyTable, no Sign‐
ingTable; (b) KeyTable, SigningTable, no Domain, no KeyFile, no Selector; (c)
KeyTable, SetupPolicyScript, no Domain, no KeyFile, no Selector.
MTA (dataset)
A set of MTA names (a la the sendmail(8) DaemonPortOptions Name parameter) whose
mail should be signed by this filter. There is no default, meaning MTA name is not
considered when making the sign-verify decision.
MTACommand (string)
Specifies the path to an executable to be used for sending mail such as that gener‐
ated by SendADSPReports and SendReports. The default is /usr/sbin/sendmail. The
executable should accept typical sendmail(8) command line options "-t" (take
addresses from message body) and "-f" (set envelope sender), accept the new message
on its standard input, and return a non-zero exit status on any error.
MultipleSignatures (Boolean)
Allow addition of multiple signatures when a signing table is in use. See Sign‐
ingTable for more information.
MustBeSigned (dataset)
Specifies a set of header fields that, if present, must be covered by the DKIM sig‐
nature when verifying a message. If a header field in this set is present in the
message and is not signed, the filter will treat even an otherwise valid signature
as invalid. The default is an empty list.
Nameservers (string)
Provides a comma-separated list of IP addresses that are to be used when doing DNS
queries to retrieve DKIM keys, ADSP policies, VBR records, etc. These override any
local defaults built in to the resolver in use, which may be defined in
/etc/resolv.conf or hard-coded into the software.
NoHeaderB (Boolean)
If set, this feature suppresses the use of "header.b" tags in added Authentication-
Results header fields. The default is "false", which means those tags will be
applied.
OmitHeaders (dataset)
Specifies a set of header fields that should be omitted when generating signatures.
If an entry in the list names any header field that is mandated by the DKIM speci‐
fication, the entry is ignored. A set of header fields is listed in the DKIM spec‐
ification (RFC6376, Section 5.4) as "SHOULD NOT" be signed; the default list for
this parameter contains those fields (Return-Path, Received, Comments, Keywords,
Bcc, Resent-Bcc and DKIM-Signature). To omit no headers, simply use the string "."
(or any string that will match no header field names). Specifying a list with this
parameter replaces the default entirely, unless one entry is "*" in which case the
list is interpreted as a delta to the default; for example, "*,+foobar" will use
the entire default list plus the name "foobar", while "*,-Bcc" would use the entire
default list except for the "Bcc" entry.
On-BadSignature (string)
Selects the action to be taken when a signature fails to validate. Possible values
(with abbreviated forms in parentheses): accept (a) accept the message; discard (d)
discard the message; quarantine (q) quarantine the message; reject (r) reject the
message; tempfail (t) temp-fail the message. The default is accept. Note that the
"t" (testing) flag in a DKIM key bypasses this behaviour; a bad signature that ref‐
erences a testing flag will still be delivered, though the added Authentication-
Results field will indicate both the failed result and the test mode so that con‐
sumers of the message can take appropriate action.
On-Default (string)
Selects the action to be taken when any verification or internal error of any kind
is encountered. This is processed before the other "On-" values so it can be used
as a blanket setting followed by specific overrides.
On-DNSError (string)
Selects the action to be taken when a transient DNS error is encountered. Possible
values are the same as those for On-BadSignature. The default is tempfail.
On-InternalError (string)
Selects the action to be taken when an internal error of some kind is encountered.
Possible values are the same as those for On-BadSignature. The default is temp‐
fail.
On-KeyNotFound (string)
Selects the action to be taken when the key referenced by a signature is not
present in the DNS. Possible values are the same as those for On-BadSignature.
The default is accept.
On-NoSignature (string)
Selects the action to be taken when a message arrives unsigned. Possible values
are the same as those for On-BadSignature. The default is accept.
On-PolicyError (string)
Selects the action to be taken when a an attempt to retrieve and evaluate the
author domain's signing policy (ADSP) is unsuccessful. Possible values are the
same as those for On-BadSignature. The default is accept.
On-Security (string)
Selects the action to be taken when a message arrives containing properties that
may be a security concern. Possible values are the same as those for On-BadSigna‐
ture. The default is tempfail.
On-SignatureError (string)
Selects the action to be taken when a message cannot be signed because of issues
with the message or the key provided for signing. Possible values are the same as
those for On-BadSignature. The default is reject.
OversignHeaders (dataset)
Specifies a set of header fields that should be included in all signature header
lists (the "h=" tag) once more than the number of times they were actually present
in the signed message. The set is empty by default. The purpose of this, and
especially of listing an absent header field, is to prevent the addition of impor‐
tant fields between the signer and the verifier. Since the verifier would include
that header field when performing verification if it had been added by an interme‐
diary, the signed message and the verified message were different and the verifica‐
tion would fail. Note that listing a field name here and not listing it in the
SignHeaders list is likely to generate invalid signatures.
PeerList (dataset)
Identifies a set of "peers" that identifies clients whose connections should be
accepted without processing by this filter. The set should contain on each line a
hostname, domain name (e.g. ".example.com"), IP address, an IPv6 address (including
an IPv4 mapped address), or a CIDR-style IP specification (e.g. "192.168.1.0/24").
An entry beginning with a bang ("!") character means "not", allowing exclusions of
specific hosts that are otherwise members of larger sets. Host and domain names
are matched first, then the IP or IPv6 address depending on the connection type.
More precise entries are preferred over less precise ones, i.e. "192.168.1.1" will
match before "!192.168.1.0/24". The text form of IPv6 addresses will be forced to
lowercase when queried (RFC5952), so the contents of this data set should also use
lowercase. The IP address portion of an entry may optionally contain square brack‐
ets; both forms (with and without) will be checked.
PidFile (string)
Specifies the path to a file that should be created at process start containing the
process ID.
POPDBFile (dataset)
Requests that the filter consult a set for IP addresses that should be allowed for
signing. This feature was designed for POP-before-SMTP datastores. (Not enabled
for this installation.)
Quarantine (Boolean)
Requests that messages which fail verification be quarantined by the MTA.
(Requires a sufficiently recent version of the milter library.)
QueryCache (Boolean)
Instructs the DKIM library to maintain its own local cache of keys and policies
retrieved from DNS, rather than relying on the nameserver for caching service.
Useful if the nameserver being used by the filter is not local.
RedirectFailuresTo (address)
Messages bearing signatures that failed to verify are redirected to the specified
address. The original envelope recipient set is recorded in the header before re‐
direction occurs. By default, no redirection is done.
RemoveARAll (Boolean)
Removes all Authentication-Results: header fields that also satisfy the require‐
ments of RemoveARFrom below. By default, only those containing a DKIM result are
removed.
RemoveARFrom (dataset)
Defines a set of hostnames whose Authentication-Results: header fields should be
removed before the message is passed for delivery. By default only those header
fields matching the local host's canonical name will be removed. Matching is only
done on full hostnames (e.g. "host.example.com") or on domain names (e.g. ".exam‐
ple.com").
RemoveOldSignatures (Boolean)
Removes all existing signatures when operating in signing mode.
ReplaceHeaders (data set)
Defines a set of header fields that should be affected by the text replacement
rules defined by the ReplaceRules setting. By default, all header fields are
included. (Note: Feature is experimental.)
ReplaceRules (string)
Specifies a file containing a list of text replacement rules that are applied to
the message header fields to replace certain content expected to be changed as the
message passes through local MTAs. This can be used to accommodate expected
changes such as are made to From: fields by MTA "masquerade" features. Each entry
in the file consists of a POSIX regular expression, followed by a tab (ASCII 9),
followed by the text that should be used to replace the text matching the expres‐
sion. The '#' character denotes the beginning of a comment and text from that
point on in a single line is ignored. Blank lines are also skipped. (Note: Fea‐
ture is experimental.)
ReportAddress (string)
Specifies the string to use in the From: header field for outgoing reports (see
SendReports and SendADSPReports below). If not specified, the executing user and
local hostname will be used to construct the address.
ReportBccAddress (string)
Specifies address(es) to include in a Bcc: header field on outgoing reports (see
SendReports and SendADSPReports below). If multiple addresses are required, they
should be comma separated.
RequestReports (boolean)
When signing, includes a request for signature evaluation failures in the signa‐
ture. (See draft-ietf-marf-dkim-reporting for details.)
RequiredHeaders (boolean)
Checks all messages for compliance with RFC5322 header field count requirements.
Non-compliant messages are rejected.
RequireSafeKeys (boolean)
When reading a key file, a message will be logged if the key file has the read or
write bit set other than for the owner or for a group that the executing process is
in. With this feature set to "true", the filter will further consider this an
error and refuse to make use of the file's contents. The default is "true".
ResignAll (boolean)
Where ResignMailTo triggers a re-signing action, this flag indicates whether or not
all mail should be signed (if set) versus only verified mail being signed (if not
set). The default is "false". (Experimental feature not enabled for this instal‐
lation.)
ResignMailTo (dataset)
Checks each message recipient against the specified dataset for a matching record.
The full address is checked in each case, then the hostname, then each domain pre‐
ceded by ".". If there is a match, the value returned is presumed to be the name
of a key in the KeyTable (if defined) to be used to re-sign the message in addition
to verifying it. If there is a match without a KeyTable, the default key is
applied. (Experimental feature not enabled for this installation.)
ResolverConfiguration (string)
Provides the given string as configuration information to the underlying resolver.
For the standard UNIX resolver, this is unused; for Unbound, the string contains a
filename that is considered to be a configuration file. There is no default.
ResolverTracing (Boolean)
Requests resolver tracing features be enabled, if available. The effect of this
depends on how debugging features of the resolver might be implemented. Currently
only effective with the OpenDKIM asynchronous resolver library.
ScreenPolicyScript (string)
Gives the name of a Lua script that should be run after all of the header fields
have been processed for a message; in particular, this is useful after all DKIM
signatures have been detected and initial evaluation has been done. The script has
access to all of the header fields and connection information and can that certain
signatures be ignored based on that information. See opendkim-lua(3) for details.
SelectCanonicalizationHeader (string)
Defines a header field name which, if present, adjusts which canonicalization will
be used to generate an outgoing signature. Overrides the Canonicalization setting
if the header field is present. The default is "X-Canonicalization".
Selector (string)
Defines the name of the selector to be used when signing messages. See the DKIM
specification for details. Used only when signing with a single key; see the Sign‐
ingTable parameter below for more information.
This parameter is ignored if a KeyTable is defined.
SelectorHeader (string)
Names a header field whose contents name the key to use when signing. The refer‐
enced key must appear in the KeyTable. @SELECTOR_HEADER_MANNOTICE@
SelectorHeaderRemove (Boolean)
Remove the SelectorHeader before signing. @SELECTOR_HEADER_MANNOTICE@
SendADSPReports (Boolean)
If true, when a policy evaluation fails and the signing site advertises a reporting
address (i.e. r=user in its policy record) and a request for reports of such fail‐
ures, the filter will send a structured report to that address containing details
of the incident.
SenderHeaders (dataset)
Specifies an ordered list of header fields that should be searched to determine the
sender of a message. The first header field found is the one whose value is used.
This is mainly used when verifying a message to determine the origin domain (for
policy checks), and when signing for deciding which signing request(s) to make. By
default, the DKIM library's internal list is used, which consists solely of the
"From" header field. See the OmitHeaders setting for a description of possible
values.
SenderMacro (string)
Use the milter macro string to determine the sender of the message. (Experimental
feature not enabled for this installation.)
SendReports (Boolean)
If true, when a signature verification fails and the signing site advertises a
reporting address (i.e. r=user in its policy record) and a request for reports of
such failures, the filter will send a structured report to that address containing
details needed to reproduce the problem.
SetupPolicyScript (string)
Gives the name of a Lua script that should be run once all header fields for a mes‐
sage have arrived. The script has access to all of the header fields and connec‐
tion information and can request DKIM verification or signing based on that infor‐
mation. See opendkim-lua(3) for details.
SignatureAlgorithm (string)
Selects the signing algorithm to use when generating signatures. Use 'opendkim -V'
to see the list of supported algorithms. The default is rsa-sha256 if it is avail‐
able, otherwise it will be rsa-sha1.
SignatureTTL (integer)
Sets the time-to-live, in seconds, of signatures generated by the filter. If not
set, no expiration time is added to signatures.
SignHeaders (dataset)
Specifies the set of header fields that should be included when generating signa‐
tures. If the list omits any header field that is mandated by the DKIM specifica‐
tion, those fields are implicitly added. By default, those fields listed in the
DKIM specification as "SHOULD" be signed (RFC6376, Section 5.4) will be signed by
the filter. See the OmitHeaders configuration option for more information about
the format and interpretation of this field.
SigningTable (dataset)
Defines a table used to select one or more signatures to apply to a message based
on the address found in the From: header field. Keys in this table vary depending
on the type of table used; values in this data set should include one field that
contains a name found in the KeyTable (see above) that identifies which key should
be used in generating the signature, and an optional second field naming the signer
of the message that will be included in the "i=" tag in the generated signature.
Note that the "i=" value will not be included in the signature if it conflicts with
the signing domain (the "d=" value).
If the first field contains only a "%" character, it will be replaced by the domain
found in the From: header field. Similarly, within the optional second field, any
"%" character will be replaced by the domain found in the From: header field.
If this table specifies a regular expression file ("refile"), then the keys are
wildcard patterns that are matched against the address found in the From: header
field. Entries are checked in the order in which they appear in the file.
For all other database types, the full user@host is checked first, then simply
host, then user@.domain (with all superdomains checked in sequence, so "foo.exam‐
ple.com" would first check "user AT foo.com", then "user@.example.com", then
"user@.com"), then .domain, then user@*, and finally *.
In any case, only the first match is applied, unless MultipleSignatures is enabled
in which case all matches are applied.
SMTPURI (string)
Specifies a URI (e.g., "smtp://localhost") to which mail should be sent via SMTP
when notifications are generated. (Not enabled for this installation.)
Socket (string)
Specifies the socket that should be established by the filter to receive connec‐
tions from sendmail(8) in order to provide service. socketspec is in one of two
forms: local:path, which creates a UNIX domain socket at the specified path, or
inet:port[@host] or inet6:port[@host] which creates a TCP socket on the specified
port and in the specified protocol family. If the host is not given as either a
hostname or an IP address, the socket will be listening on all interfaces. A lit‐
eral IP address must be enclosed in square brackets. This option is mandatory
either in the configuration file or on the command line.
SoftwareHeader (Boolean)
Causes opendkim to add an "DKIM-Filter" header field indicating the presence of
this filter in the path of the message from injection to delivery. The product's
name, version, and the job ID are included in the header field's contents. Note
that the header field is not added if the Mode setting causes the message to be
ignored (e.g., if only signing mode is enabled and the configuration causes the
message not to be signed, or only verify mode is enabled and configuration would
otherwise have caused the message to be signed, then it will not have this header
field added).
Statistics (filename)
This specifies a file in which to store DKIM transaction statistics. See opendkim-
stats(8) for a mechanism to parse the file's contents, and opendkim-importstats()
for a mechanism to translate the file's contents into SQL database insertions.
(Note: Feature is experimental.)
StatisticsName (string)
Defines the name to be used as the reporting host in statistics logs. By default,
the local host's name returned by gethostname(3) is used. (Note: Feature is exper‐
imental.)
StatisticsPrefix (string)
When AnonymousStatistics is enabled, this string may be specified and will be
prepended to all data before hashing for more complete anonymization. This means
two records from different sources referencing the same source will still produce
different hashes, meaning such correlation is now only possible within the data
from a single repoter.
StrictHeaders (Boolean)
If set, instructs the DKIM library to refuse processing of a message if the header
field count does not conform to RFC5322 Section 3.6.
StrictTestMode (Boolean)
Selects strict CRLF mode during testing (see the -t command line flag in the opend‐
kim(8) man page); messages for which all header fields and body lines are not CRLF-
terminated are considered malformed and will produce an error.
SubDomains (Boolean)
Sign subdomains of those listed by the Domain parameter as well as the actual
domains.
Syslog (Boolean)
Log via calls to syslog(3) any interesting activity.
SyslogFacility (string)
Log via calls to syslog(3) using the named facility. The facility names are the
same as the ones allowed in syslog.conf(5). The default is "mail".
SyslogSuccess (Boolean)
Log via calls to syslog(3) additional entries indicating successful signing or ver‐
ification of messages.
TemporaryDirectory (string)
Specifies the directory in which temporary canonicalization files should be writ‐
ten. The default is to use the libdkim default location, currently /tmp.
TestDNSData (data set)
Provides a data set whose keys will be treated as DNS record names and values as
TXT record contents. Intended for use during automated testing.
TestPublicKeys (string)
Names a file from which public keys should be read. Intended for use only during
automated testing.
TrustAnchorFile (string)
Specifies a file from which trust anchor data should be read when doing DNS queries
and applying the DNSSEC protocol. This is currently ignored unless the underlying
library is compiled to use Unbound; see the documentation at at http://unbound.net
for the expected format of this file.
TrustSignaturesFrom (dataset)
This value consists of a set of domains that are considered trustworthy in terms of
third-party signatures. That is, if a message arrives with a signature from a
domain that doesn't match the domain in the From: header, this setting determines
whether or not that signature will be trusted. If this value is undefined, all
signatures are trusted.
UMask (integer)
Requests a specific permissions mask to be used for file creation. This only
really applies to creation of the socket when Socket specifies a UNIX domain
socket, and to the PidFile (if any); temporary files are created by the mkstemp(3)
function that enforces a specific file mode on creation regardless of the process
umask. See umask(2) for more information.
UnprotectedKey (string)
Instructs the filter to treat a passing signature associated with a key found in an
insecure (i.e. not protected by DNSSEC) DNS record in a special way. Possible val‐
ues are neutral (return a "neutral" result), none (take no special action; this is
the default) and fail (return a "fail" result).
UnprotectedPolicy (string)
Instructs the filter to treat an ADSP policy found in an insecure (i.e. not pro‐
tected by DNSSEC) DNS record in a special way. Possible values are apply (apply
the policy; this is the default) and ignore (ignore the policy).
UserID (string)
Attempts to become the specified userid before starting operations. The value is
of the form userid[:group]. The process will be assigned all of the groups and
primary group ID of the named userid unless an alternate group is specified.
VBR-Certifiers (string)
The default certifiers if not specified in X-VBR-Certifiers header field. (Note:
Feature is experimental.)
VBR-PurgeFields (string)
If set, arranges to remove X-VBR-Certifiers and X-VBR-Type fields on messages prior
to sending them. (Note: Feature is experimental.)
VBR-TrustedCertifiers (string)
A colon or comma sparated list of trusted certifiers to accept when verifying VBR-
Info header field. (Note: Feature is experimental.)
VBR-TrustedCertifiersOnly (Boolean)
By default, the certifiers that are in both the trusted certifiers list (above) and
those in the message's VBR-Info header field will be checked for vouching. With
this option set, the trusted certifiers will be checked and the ones claimed by the
message will be ignored. (Note: Feature is experimental.)
VBR-Type (string)
This default VBR type if not specified in the X-VBR-Type header field. (Note: Fea‐
ture is experimental.)
WeakSyntaxChecks (Boolean)
Requests that the library continue processing messages even if syntax errors are
discovered early in message analysis. This means, for example, that a signed mes‐
sage with a mangled From: field will still proceed to verification even if the
author's domain could not be determined, which makes later ADSP checks impossible.
NOTES
When using DNS timeouts (see the DNSTimeout option above), be sure not to use a timeout
that is larger than the timeout being used for interaction between sendmail and the fil‐
ter. Otherwise, the MTA could abort a message while waiting for a reply from the filter,
which in turn is still waiting for a DNS reply.
Features that involve specification of IPv4 addresses or CIDR blocks will use the
inet_addr(3) function to parse that information. Users should be familiar with the way
that function handles the non-trivial cases (for example, "192.0.2/24" and "192.0.2.0/24"
are not the same thing).
FILES
/etc/opendkim.conf
Default location of this file.
VERSION
This man page covers version 2.9.2 of opendkim.
COPYRIGHT
Copyright (c) 2007, 2008, Sendmail, Inc. and its suppliers. All rights reserved.
Copyright (c) 2009-2013, The Trusted Domain Project. All rights reserved.
SEE ALSO
opendkim(8), opendkim-lua(3), sendmail(8)
RFC5451 - Message Header Field for Indicating Message Authentication Status
RFC5617 - DKIM Author Domain Signing Practises
RFC5965 - An Extensible Format for Email Feedback Reports
RFC6008 - Authentication-Results Registration for Differentiating among Cryptographic
Results
RFC6376 - DomainKeys Identified Mail
The Trusted Domain Project opendkim.conf(5)
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