Ask YC: What mail server do you use?

Postfix - easy to setup & better security model than sendmail.

Dreamhost hosts my mailbox. I have a nice setup that runs server-side where SpamAssassin automatically trains CRM114 and the two check each others' results and make sure they don't produce opposite conclusive answers. I use mutt as an MUA and Postfix as an MTA, with DynDNS's outbound mailhop service to get around the firewalls imposed by various lame ISPs.

google apps myself, I haven't hit the limit. Just create more users and append a # (noreply1,noreply2) to the end of them. I thought I read that was google's answer for when your breaking the limit.

Question for you, what are the limitation, besides this, you've had with google apps mail servers?

I currently run a mail server for a client, though I rarely use it for my own purposes. It's Exim.

Postfix (managed by Virtualmin and Webmin, of course).

For outgoing mail, I use the IIS SMTP service. For incoming postfix + courier is great, but people are making noise about exchange (ugh).

I've got a somewhat related question: If a bunch of guys that were used to Exchange and the internal calendaring/syncing with phones/etc. left, and wanted to break their MS bonds and embrace oss, what would they use? Basically - is their a compelling alternative that would still work with Blackberry?

Free gmail for own domain

I use courier right now. But I've migrated from courier to dovecot for pop3/imap, and I'm planning to migrate from courier to postfix for smtp. Courier is just too limited.

Three separate Postfix instances running on the same server, albeit bound to separate IP addresses and tweaked for their particular use.

Google Docs - Free version (Gmail with own domain)

webmail.us, the best.

Curently writting my own in Erlang ... again ...

can't go wrong with postfix

qmail

Some registrars also offer e-mail service, like GoDaddy. It's much cheaper than webmail.us but you don't get as much storage.