Crash trying to send email

was seen in Warning: Could not load file or assembly WindowsBase, Version=4.0.0.0 and confirmed fixed by installing mono-complete rather than a smaller package like mono-devel,. That might at least avoid that warning, and I have no idea whether it would help whatever’s wrong with email.

You could test a profiling log with a small backup, because a big backup will produce an enormous log file. As mentioned before, doing the small backup on true CLI might also reveal more, but no promises on that.