[CentOS] centos email server suddenly much slower. What to do?

Thu Sep 6 21:42:58 UTC 2012
Laurent <laurent at tnpl127.net>

Le 2012-09-06 19:14, Marco Fioretti a écrit :
> 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

> 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?

My 2 cents. You probably checked a lot of things.

- a filesystem (almost) full ?
- did you check the logs ? any errors ?
- a user sending/receiving a large e-mail ? what is the maximum size of 
an e-mail in your MTA settings ?
- more mail-services-related processes ?
- did you try to stop mail services to see if the server usability is 
back ?
- do you run antispam and/or antivirus on incoming/outgoing e-mails ?

- to help with DNS, you can probably enable nscd or setup dnsmasq, so 
it would reduce DNS queries sent to DNS servers.