imap putting mail in local sent folder despite defaults

Hi guys, hope someone else has figured this irritating one.

It is occurring with both Thunderbird and Outlook, and only on selected machines, not all of the network. But only on Win7 64.

Intermittently the sent mail will be placed in the local sent folder rather than the IMAP sent folder. Most of the time the mail that this happens to, happens to have an attachment. This is causing some users to check that it was sent and not see it in the sent items, then send it again, and again (even though it is sending every time), causing confusion for all involved. It may be one mail in 50 that this happens to though, or 3 in one day from one user.

It's not a life ending bug, but I don't like these things hanging around. I've googled and can't seem to get any hits on the same problem, maybe getting my keywords wrong.

Can anyone help please?

Edited by hamluis, Yesterday, 07:05 AM.

Moved from Business Applications to Web Browsing/Email - Hamluis.

via Bleeping Computer Last 20 Posts http://www.bleepingcomputer.com/forums/t/513291/imap-putting-mail-in-local-sent-folder-despite-defaults/