On Thu, Sep 6, 2012 at 12:14 PM, Marco Fioretti marco.fioretti@gmail.com wrote:
Greetings, I run my own email server for some domains I administer, on a centos vps server with a very small number of users.
The only services are smtp, imap/pop, webmail
Everything was running without problems until this morning. I left home for 1/2 hours, and when I came back everything had become about 100x slower (seriously!). The services were/are still all up and running, but practically unusable (even running mutt in my ssh session is almost frozen).
I have not changed/updated anything in the last 1/2 weeks. I have already done a few checks with the VPS provider, and it looks like:
network & hardware are OK
there seem to be no strange processes running. I didn't manage to save the output of "top", but it didn't show anything that (AFAICT, of course) should not be there on an email server
however, there is something that is using "much more memory than normal" (see the comment below from the hosting sysadmin after he checked user_beancounters). Initially we thought it was apache, but even switching it off didn't change anything. What now?
Any help to understand what the heck happened, and find out what exactly _started_ to cause this problem is very welcome!
One thing to check is that the DNS servers in /etc/resolv.conf are answering quickly (dig some_name.domain @server_ip). Mail services use DNS extensively and if the first server fails there is a timeout before trying the 2nd choice. Things will still work but slower and you may end up with enough processes running to run out of RAM and start swapping. Also check your outbound mail queue in case some spam attempt has succeeded in generating bounces.