Outlook stops refreshing and seems to hang on connection

Since a few weeks Outlook seems to have a problem.

There is no error message that is appearing, that's what makes it difficult.

Closing Outlook and opening it again solves the issues, at least for a short time (1h or so).

The problems is recognizable like this:

- Reply to an Email, a new Email opens, but the content of the old Email does not load or get included.

- Emails you send won't get out. I've found a "Email could not be sent right now" message in the outbox, no reason why.

- if i archive mails in the inbox, they dissapear, but suddenly come back when i restart outlook

It seems like the user interface is still working, but actions do not resemble serverside.

No error message. 

Anyone experiencing the same thing?