In the beginning of this year, we’ve decided to replace our old mail server, which was pretty at the end of its capacities, dealing with as “little” as 50’000 new mails (sent & received) DAILY for our 1500 mail users.
With also about 800’000 single mails stored, the old mail server ran out of disk space; we surely needed A LOT of disk space and even room for storage expansions.
In may 2008, we evaluted a few server-configurations and finally decided for a Dell 2950, with which we already had good experience from the DB-Servers.
Although they are not as fully equipped as the DB-Servers, it’s a pretty nice configuration for a mailserver; this should allow us to handle all the fast increasing mails for the next few years:
- Quad-Core Xeon E5430 2.66GHz/2x6MB
- 8GB RAM (2X4GB dual rank DIMMs)
- 4 x 146 GB SAS 15k 3.5″ HD (RAID 5); two mounts free for storage expansion
- Redundant Power Supply
As operating system we installed CentOS 5.1 Linux.
For comparison, our old mailserver was running with Gentoo (since january 2006) and had the following hardware specifications (manually built with self choosen components):
- Dual P2 2.66GHz
- 2GB RAM
- 2x 160GB IDE 7.5k 3.5″ HD (with Software Raid 1)
- SinglePower Supply
- 3 unit iron chassis
Just to say, at this time the mailhost was used for a few dozen accounts and never mentioned to handle a lot of mails or accounts.
Basically we wanted to integrate our actual configuration as good as possible, this included:
- postfix as SMTP Server
- courier as IMAP/POP3 Server
- Maildrop / ClamAV / Spamassassin for filtering anti- virus and spam
Unfortunately two of these components weren’t able on CentOS; namely courier and maildrop.
For maildrop it was however possible to compile an rpm “out of the tar-archive” and for courier we’ve decided to replace it completely by dovecot, rather than “hacking” courier into the system by custom compile it – Too much upgrade hassles for a highly productive system.
In the process of migrating, we also decided to replace the Cyrus-SASL daemon for authentication, because I wanted something documented and functioning – this are definitely not things to describe Cyrus-SASL.
Instead of, I wanted to do all authentication (SMTP and IMAP/POP3) trough the dovecot server, which has a very clean authentication daemon.
Nice plan, but we still stepped into the problem, that we couldn’t learn maildrop how to authenticate with dovecot-auth; instead we had to install courier-authlib for maildrop. -As, they use the same data-source for user-information anyway, it wasn’t really a big deal.
Next we also wanted to enforce the quota limits now, which was quite easy with dovecot and maildrop. For squirrelmail there is also a nice quota-plugin available which shows the quotas in webmail.
After a lot of testing, we finally migrated the new mail server yesterday and it even functioned from the beginning, with almost no interruption.
Finally some new advantages we have on our new mailserver:
- Raid 5 for secure and reliable storage
- Redundant power supply with autonomous USV machines to prevent outages
- Daily backup of every mail message to 3 different servers
- FAST mail delivery: Our statistics show us, that the new mailserver is more than 10 times(!) faster than the old one.
- Various configuration tweaks, made possible with new software and the improved hardware, ensure that we receive much less incoming spam than before
- Extensive spam and virus filtering
- Stable smtp, imap and pop3 services which we can trust
- Quota: We have now introduced our new quota feature