There is no email quota. email storage is included within the total storage.
Most email don't take much space. When it does, (attachments etc.) it is not a problem.

Email have full web based access, and standard POP3 access. IMAP access is included,
which is convenient to access the same mailbox from multiple locations.
Each user has its own password and separate mailboxes. SMTP outgoing mail is available.

Email include autoresponders, dispatchers, internal mailing list (no spam).
Email redirection, internal or outside is available anytime at the user's decision.
Also access to procmail, formail, database driven email, and programer interface.
Email can be automatically filtered for spams, virus, worms.

Traffic is usually not an issue for most sites. However, if your site becomes sucessfull,
no problem, it can handle any additional traffic. Same apply to storage if larger space
need arise.

Webalizer web statistic is installed and updated daily.
Overall Storage and traffic graph and measurement are available anytime
for self-served control, easily all from the web.

Group of users can be easily managed. 

One Shell account is provided with each plan. It includes full SSH access.
ftp, sftp, scp (secure ftp) is available on all account.
More shell account and group ownership of files is also available.

The user is expected to have some familiarity with the internet. Technical support
is available to all accounts.

Extensive programming environment is available:
Perl, PHP, Python, TCL, C, C++, Bison, ruby, and other languages.
CGI, SSL, PGP, engryption and suexec are securely installed and available to all.
MySQL, PostGreSQL, OpenLDAP  Databases, with libraries, modules ready to use
for the programmer.

Apache is the web server, installed with all standard modules, user cookie track,
mod-rewrite and other extended modules. full access to all directives in htaccess.

The Web-centric user control:
Email read and send. email fetch from other accounts.
File manager. zip/unzip from the web.
Database control.
Group management.
Domain name edit and management.

Important features:
* Web-centric user control with extensive flexibility.
* Group sharing and data management.
* Secure by default on all services.
* Full scalability of account.
* Technical support.
* Secure shell access.
* All email facilities supported.
* User friendly access.
* Programer friendly environment.

RootRoute is a good choice.