[imp] random logouts IMP 3.1

[Clarence Feng]

We've been running IMP 3.1 for a bit over a year, and while generally 
stable, the number of complaints about an odd problem have increased 
since last Spring. The typical complaint is:

User logs in, and when doing normal operations (reading email, 
compose email) the user clicks on a link or button that will cause 
IMP to do something (send mail, open message) and suddenly finds 
themselves logged out with a message that their session has expired. 
This problem was not as much in evidence until the last six months, 
but we've made no major config changes or upgrades in that time.

Users sometimes cannot log back in, apparently because browser 
continues to send a session ID that the server interprets as expired. 
Sometimes exiting and relaunching the browser helps.

We have researched via google a number of threads regarding IMP 
session files and timeouts, and have done the following:
- Altered php.ini to turn off session based cookies- this supposedly 
mean authentication is done by URL according to list archives.
- Changed document expiration time to three hours
- Changed garbage collection time to two hours
- Altered IMP code in accordance with this message found in IMP archives:
http://lists.horde.org/archives/imp/Week-of-Mon-20020617/022817.html

Some info:
IMP 3.1
PHP 4.2.0
Apache 1.3.26

We are considering bringing up a front-end server with IMP 3.2, but 
are hoping an answer exists for the problem in 3.1 so that user's 
will have reasonable utility with IMP. I'm down to grasping at 
straws, so if there are any suggestions, I'm all ears.

Clarence Feng