SMTP only

==== Required information ====
- iRedMail version: 0.8.6
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Linux/BSD distribution name and version: Deb 6
- Related log if you're reporting an issue:
====

I would like to have a send only account on my server.

And I don't want to store the sent emails. So, the account should just relay the emails.

How do I achieve this?