The version of Outlook that I use is: Microsoft Outlook for Mac 2011 - version 14.2.0.
I have read other posts on the same topic, but so far nothing fixed the problem.
I keep receiving from a couple of dozens to more than one thousands emails (previously received) every month or so. It tends to be all the emails for one month, and if the problem does not occur for 3 months, then it will be all the emails for 3 months, etc. This does not happen on the web, only on outlook. I have not found any virus on my computer. I have not found any blocked email in the outbox.
I have recently transferred all the contents of my MacBook Air on to a new MacBook Air but the problem occurred on both computers and never stopped.
Also, when I re-start the computer, 2 draft emails dated March 15 appear on the screen though I trashed them a long time ago.
Thanks for your help!