[imp] IMP memory consumption

[ibj at earthlink.net]

I've recently installed Horde, IMP and Turba on my web server. It's a very impressive application, and everything seems to be working flawlessly, but I'm concerned about the memory consumption. Each time IMP is started, or the INBOX is refreshed, between 2-4MB of available system RAM is consumed. This appears to be gradually released back to the system after the IMP session is terminated, but what will be the effect if many users were to access their mailboxes concurrently? I'd like to avoid disk-swapping as much as possible.

I thought the culprit might be the POP3 software, but accessing the POP mailbox from other mail clients doesn't produce this memory drain. Could this be a configuration setting that I've set up improperly, or is it normal behavior? I'd appreciate any thoughts or suggestions!

System configuration:

Dual Xeon 2.0G processors w/ 1GB RAM
Redhat Linux 7.3 (2.4.18)
PHP version: 4.3.3 w/ Zend Optimizer
Web Server: Zeus 4.2r2
Horde 2.2.4
IMP 3.2.2
Turba 1.2.1
POP3 server
MySQL backend for Prefs, Turba contacts, custom session handler

Thanks!