My distribution is Mandriva 2009/Cooker with KDE4 4.1.80, Kontact version 1.3 and KMail 1.10.90.

Recently I've noticed that after start KMail (with Kontact) lockups for very long time causing one CPU's core load at 50% and hard drive to work very intensively.
Any operation on mail (changing folder or message) takes minutes.
After ~10 minutes everything settles down beside one or more pop-ups saying that:

Your POP3 server (Account: name of one of accounts) does not support the UIDL command: this command is required to determine, in a reliable way, which of the mails on the server KMail has already seen before;
the feature to leave the mails on the server will therefore not work properly.

while all work normal.

After that everything is OK for some time (or till next restart).

My e-mail box is around 4.5 GB big and I'm storing lots of e-mails.

Is there anything I can do to make the lockups go away?