Hello

I've been seeing a strange issue with Thunderbird IMAP in combination 
with MSU Mail.  Their Sent messages are split into folders by month, 
without the user doing anything.  I can't find an option in Thunderbird 
or mail.msu.edu that would explain it, and this is happened to two 
people so far.  One day all their Sent messages where in one folder, and 
the next day, they had moved into folders according to month underneath 
the Sent folder.

Any ideas?