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I have the following situation: I have a home server running debian stable that handles my emails. It is a getmei/postfix/courier combination. On my desktop PC I use debian stable with kde and as mail client kmail/kontact (as imap(s) client). The server stores the mails of several mailing lists, so there are quite a lot of mails in my mail folder (maildir format).

Some days ago I noticed that kmail takes a long time to get the content of a folder on the imap server. Even after 15 min there was no result there. On looking on the server CPU, I found that the CPU load is at approx. 50% for some minutes and the hd is working quite hard (Acoustically and via iotop).

The result is, that I cannot access some folders on the imap server anymore. These folders are nearly empty! That means this cannot be a problem of dozens of mails in this folder.

After some time (2 or 3 min) the cpu load drops but kmail still waits for the results from the server. Normally I have to manually break kmail vis SIGTERM as it hangs now and then as this happens.

Now I do not know why courier has this high load and why it does not answer the kmail query correctly.

What can I do to

  • get the reason for the high load?
  • solve the problem?
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What do the logs say? dmesg, courier logs? – Bobby Sep 12 '12 at 9:59
Hello, sorry for the late answer, my ISP did nasty things.... I did not find anything about courier in syslog or dmesg. How to enable courier verbose log? I did not find anything in the config files. – Christian Wolf Sep 17 '12 at 7:50

So, I found the solution myself, though it was not a courier problem.

I has an error in my dns lookup table which had the effect, that kmail tried to connect to a host in the internet that does not be the correct server.

After removing the error in DNS all went right. Ish happens!

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