I had a problem for over a year now with a mail account hosted on my ispconfig server.
The first thing I noticed was that there was a phantom folder with no name under my email account.
Then after it performed a Send and Receive, Outlook would crash.
It turns out that there was a bug in ispConfig 18.104.22.168 that inserted a extra line break in the Mail Subscription file. Even though I was running 22.214.171.124, my email was created while in the previous version.
Remove the first line and save. :qw