We have email installed on our Nethserver and we use Webtop as our webmail platform installed on Nethserver.
I may have a lead here (not sure how I missed in my initial search of the forums). This post references a similar problem where users were deleted from Nethserver but Webtop Admin still had the users listed. I looked in my Webtop and I couldn’t see the two deleted usres in my “Users” table…but I did find them in my Webtop “Groups” table. I’ve deleted them from Groups. Now I’ll wait a few more minutes to see if the error logs stop in my Nethserver Logs.