Problem partially solved.
The crashing of Outlook 2007/2010 (does not happen with 2003) was resolved by removing the blank line at the top of the subscription file in Maildir for each user. Apparently, Outlook could not handle this.
The problem now is how to correct it for all new email users.
I assume there is a place somewhere that the code to create the subscription file can be edited.
Anybody know where it might be?
I am using ISPConfig 188.8.131.52