The timestamp of main.srt changes if a user deletes a message via webmail, which will give you some positive activity info. But unfortunately, the timestamp isn't changed if the user just reads mail, so that's not going to get you all the way.
I bet you could write something into the webmail pages--probably, Ron from HKSI already has--to touch a last-logged-in placeholder, maybe even reusing the otherwise untouched userdict.tlx or main.srt for this purpose, file whenever the user logs in. Then you could scan the dates of said files. Sandy Please visit http://www.ipswitch.com/support/mailing-lists.html to be removed from this list. An Archive of this list is available at: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/
