we are currently thinking about running a medium size mail service.

Currently, dovecot seems to be the a good fit and we are about to setup a small test environment to check out some integration points with other systems. However, I was wondering if there are any good alternative mail servers (or services) that we haven't looked at yet (we've also looked at qmail). The alternatives doesn't exactly have to be free or open source but we do have some requirements.

Must haves:

  • Must support delegation of user authentication to a centralized user registry.
  • Must support between 50K and 150K users.
  • Must support configuration of mailbox/outgoing/incoming mail size.
  • Must support integration with an ingoing/outgoing spam/malware filter.

Optional (but much appreciated):

  • Should have a API (preferably a cross platform one like a REST service or an open database) to allow querying of user stats like quota usage, spam status, unread mails etc., for use in other applications.
  • Should have support for SSL-connectivity.

It seems as though Dovecot is a nice fit and I'm mostly just looking for confirmation that this is the right choice, or if not, what we should look at instead.


Dovecot is a perfectly nice POP/IMAP server. Cyrus may also meet your needs. I've worked with both; I think that you'll probably find Dovecot easier to work with. Cyrus has some interesting support for clustering (spreading your mailbox load across multiple backends) that may be of interest if you're handling lots of traffic.

  • Would you consider +25K daily users "lots of traffic"? – JohannesH Jun 8 '11 at 20:01
  • I don't know. I don't have any idea how that translates to load in your environment. I believe there are tools our there for stress-testing your IMAP server if you want to test out various solutions and see how the performance compares. – larsks Jun 8 '11 at 20:05

Dovecot works nicely and integrates with LDAP or SQL. Dovecot can also be used for mail delivery and as an authentication backend for an SMTP server such as postfix.

I'd recommend you look into dovecot, Dovecot Director for clustering and postfix for SMTP. Maybe also postfixadmin for SQL based user management.

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