Question

I appreciate there is no ‘set’ answer to this question. I am trying to assess the performance of our dedicated mail server for sending out emails. The server is of the spec below:

• 2G RAM
• CPU Xeon 2.80GHz (x2)

Currently we’re only managing to send out approximately 21,000 emails per hour from this. Which I suspect is massively under-performing.

Are there any guidelines as to what capacity can be expected?

Answer 1

Actually it also depends on the configuration. For exxample, if you use amavis, spamassassin or clam or another content filter it will directy affect the performance.
If you do no use any contentfilter, you should have capacity limit higher then 21,000 emails/hour.

Another point is queue size. If you have a growing queue you have a problem. If the queue is steady, no need to worry. Check queue size with “mailq | tail -1”

Check some params:
default_destination_concurrency_limit = 40
initial_destination_concurrency = 5
lmtp_destination_concurrency_limit = $default_destination_concurrency_limit
local_destination_concurrency_limit = 10
relay_destination_concurrency_limit = $default_destination_concurrency_limit
smtp_destination_concurrency_limit = $default_destination_concurrency_limit
virtual_destination_concurrency_limit = 35

Check master.cf 

smtp      inet  n       -       n       -      300      smtpd
smtp      unix  -       -       n       -       -       smtp

smtpd is for incoming limit
smtp is for outgoing. If 7th field has a value this will limit concurrent server processes.

You can check google for further analysis.
http://www.google.com.tr/search?q=postfix+performance&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:tr:official&client=firefox-a