Hi,
What OS and mail server are we talking about here? I have experience with linux / bsd systems running qmail. Our initial setup was based around text files. There was just 1 pop user ID which maintained virtual users.
Updates were performed by a sudo-privileged user which apache was run as. The only issue was file locking. For example:
o user_add.php locks : popuser
o user_delete requests lock on different apache thread, initial file lock broken.
The lock is maintained for user_add requesting another lock. You have been warned! This was my experience with 4.0.6, with 4.3.0 we're on a different format -- read on 🙂
All admin functions had to be hence maintained via one control file.
We recently moved to vpopmail and retained our control panel functionality by sending curl based ssl requests to mail daemons in bsd jails. This works very well with vpopmail functions. The mail server now acts as an xml gateway accepting requests from the control panel IP address.
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If this sounds like the way you would like to proceed, I can assist with setup and layout specs. Unfortunately, I cannot make the code available.
Also: if you need to speak on the phone to clear some issues, don't hesitate to ask.
However, if this is not something you want to pursue, have a look at control panels like qmailadmin (if you're running qmail) and other such utilities for mail servers.
Hope this helps.
Finally: this may be all you need! http://www.plesk.com
-m.