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What kind of servers do I need to run SpamAssassin for my large site?

Obviously, every site is different. Here are some details on one large scale deployment that you may find useful as a benchmark.

MWEB is the largest ISP in South Africa, with approximately 350,000 mailboxes, all of which get filtered through SpamAssassin.

Their setup entails 8 servers running Postfix, 12 servers running amavisd-new, and an additional 5 servers running Trend Micro and Vexira anti-virus. Their 25 servers are Dell Power Edge 2650's with dual 3.0 GHz Xeons, 4 gigs of ram, and 5 SCSI drives in a RAID 10 configuration (1 hotspare). They're running a custom built Fedora Core 2, 2.6.7 kernel .

Here are their statistics for April:

Year  Month Messages Blocked  Messages Passed  Total Messages  Percentage Blocked 
2004   Apr     106,710,305     25,065,604       131,775,909         80.98 % 

Thus, their long term average is 131,775,909 / 30 / 24 / 60 / 60 = 50 messages per second. Their peak rate is up to about 300 messages a second, or 6x their average.

Note that while amavisd calls Mail::SpamAssassin directly, it runs Perl as a daemon and should offer performance quite close to spamd. This suggests that a single brawny server running spamd can comfortably handle 5 messages a second and may peak up to 30 messages per second.

More info

Please contribute details on your large installation. It's fine to do so anonymously if necessary.


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