Outlook 2013/2010 nightmare

[Jakob Curdes]

Just a basic comment: Outlook is well known for its bad IMAP support.
It is really not a recommendable IMAP client. My experience is similar 
to yours: it may work, then it may not work, while other clients can use 
the same account without problems.
Essentially I think Outlook always beleives what it has on-disk for the 
account rather than believing the IMAP server, which leads to very 
strange situations. The issue you describe could be related to this.

Regards, Jakob