What are the reasons for using ctime instead of mtime for
autopurge stuff in your webmail?
mtime can be manipulated by an IMAP client.
Hm. Is it a only one reason? I ask a question, because it seems
that IMAP client can change also ctime, for example while looking
for the new messages in the folder.
It can be some confusing for users, because when they log
into the webmail, then it moves all messages from new/
to cur/ directory and ctime of the files is changed,
of course. In the result, autopurging of some old files
in Trash folder can be delayed.
And some may consider it an added feature. If you don't care about
the trash, everything gets purged on time. If you open it, the most
recent trashed files get an extra lease on life.
OK, it's acceptable for me ;)
But I have only one little note here: a user haven't to open
his Trash folder, because your webmail moves trashed files
from .Trash/new to .Trash/cur folder also when a user log into
the webmail successfully.