Hi
during times of high mail load, spam attacks usually, I sometimes run into an issue where postfix will stop responding or becomes extremely slow on the stmp port. In turn this causes my pop/imap server (dovecot) to stop responding or to become extremely slow as well. When I stop postfix, the pop/imap server go back to normal. I have 3 email filter servers that scan the email before delivering it to the postfix server. When the problem occurred I did notice with netstat that there was a huge number of established connections on port 25 with the mail filter servers on the postfix server. The thing that I don't understand is that before the problem occurred I had "smtpd_client_connection_count_limit = 30" which was working with no issues . When the problem started to occur I saw exceed errors on the mail log, basically connection numbers over that limit of 30. I was seeing upwards of 70 connections per email filter host. When this started happening ports 25/110/143 became extremely slow. My question is if I have a smtp client limit why do still see so many established connections with netstat. Shouldn't postfix stop the extra connections? (the email filter servers are not part of $mynetworks) Why is postfix slowing down my pop/imap server when this occurs? This is extremely busy server with plenty of CPU and memory, what is a reasonable smtpd count limit that will not overwhelm the server? FYi, when I changed that smtpd client connection to 100, the problem went away and all was good again. mail_version = 2.6.5 250-PIPELINING 250-SIZE 26000000 250-VRFY 250-ETRN 250-AUTH LOGIN CRAM-MD5 PLAIN DIGEST-MD5 250-ENHANCEDSTATUSCODES 250-8BITMIME 250 DSN Thanks Paul
