I'm probably going to have to scale our mail system (not really just a
mail "server" anymore :-) a bunch in the coming months, and am looking to
get any advice from others that are running largish mail systems.
Right now I have several inbound MX boxes that do spam/virus filtering and
accept mail from the outside world. They all deliver to one beefy server
with a big RAID that stores the mail (we call it the mailstore server),
and handles POP3/IMAP connections from users. There is a seperate webmail
server running squirrelmail, and another server with a fast RAID 10 that
does all the outbound SMTP and takes messages in from users and bounces
from the other servers.
The whole thing is qmail/vpopmail based, with spamassassin and clamav on
the inbound MXes. Right now we're planning on splitting out the MySQL
stuff (right now that runs on the mailstore server) onto 2 or more
MySQL-only servers since they handle a lot of queries for vpopmail (MySQL
backend), squirrelmail (user prefs), and spamassassin (user prefs).
We'd like to be able to scale the system with minimal use of hardware load
balancers due to cost. Most of the examples I see out there use a big
server running NFS and several smaller servers that handle user queries
for POP/IMAP/etc., but it seems like that would have some issues keeping
sessions with authentication, and most of the examples are out of date.
Our inbound works great -- we can just add more MX servers, but I'm
concerned about the POP3 and IMAP connections, and possibly the outbound
SMTP if we need more than one server.
Does anyone have some expierience to share or maybe a link to some newer