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I am having a problem with the average server load on my godaddy VDS getting as high as 50. The culprit is all the smtpd processes. If I kill postfix the server load will drop down to about 0.7.

This server is not an open relay. I added the following to main.cf to prevent that.

smtpd_helo_required = yes
smtpd_delay_reject = no
disable_vrfy_command = yes

My theory is that even though the server is rejecting relaying it is still being bogged down due to the enormous amount of relay attempts. I just started the mail logging under an hour ago and the file size has went from zero to 8.0M in that time because of all the relay attempts. Would these attempts even though rejected be able to considerably add to the server load? If so how can I remedy this?

Here is a typical rejection in the log.

Jul 30 17:01:43 ip-xxx postfix/smtpd[7555]: NOQUEUE: reject: RCPT from tdev193-211.codetel.net.do[200.88.193.211]: 554 5.7.1 : Relay access denied; from= to= proto=ESMTP helo=

I am by no means adapt at mail server configuration. I will be happy to provide any further informtation needed to zero in on this problem.

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2 Answers 2

Your theory sounds correct, as that source appears in Spamhaus's XBL, so likely up to no good.

You could try rejecting the mail sooner, when the client connects, rather than waiting for the RCPT TO to reduce the load.

Depending on the purpose of the server, other access restrictions might help.

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Thanks for the solid links. If I had the rep I would vote this up. –  Christian Thamer Aug 1 '10 at 5:40

Also, you can throttle the number of simultaneous Postfix processes to keep it from bogging down everything else. This will be particularly useful if Postfix is using enough RAM to cause swapping (and actually, it may increase the number of attempts you can handle rather than decreasing it). It may still help, though not as much, if your high load is from CPU usage from all the connections. It means some attempts to send you mail will fail, but any sender that's not a spammer will retry multiple times.

Check http://www.postfix.org/postconf.5.html#default_process_limit for details. Also check the section for master.cf linked from there (I'd link it, but apparently I don't yet have enough reputation to post multiple links)

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