[imp] urgent problem with IMP (i guess)

[matiss at jekabsons.lv]

Hallo!
First of all i am using horde groupware webmail ed.
Sometimes our webmail is reaaaallly slow. And it seems that this  
slowliness is caused by... sql or php(?)
There are only 20 clients that are using this webmail. But it looks  
like that with more users online is more slow server. Mabey you can  
give me some sugestion to look at?

Server is:
HP ProLiant ML310 G4
Dual-Core Intel® Pentium® D Processor 945 (3.40 GHz, 800 MHz, 2 x 2MB L2)
PC2-5300 DDR2 2GB
Hot plug Serial ATA HDD 7200rpm

Best regards!
And thx for your help!
Matiss