I am terribly sorry! Rated 5 out of 5 stars

The Mail Summaries add-on is working perfectly. The bug with thread-pane columns was caused by uncompatibility bug from the CompactHeader add-on. That bug was fixed in today's CompactHeader update.

Thank you for your work!

This review is for a previous version of the add-on (2.0).  This user has 2 previous reviews of this add-on.