SUMMARY
When I do a large operation on a folder (delete messages, mark as read, etc on hundreds to thousands of emails) I cannot look at or do anything else with mail until it completes, not even in a different folder or different email account. I get the "Retrieving folder contents" message and have to wait (many minutes). It is acting as if Kmail or Akonadi is only single threaded.

STEPS TO REPRODUCE
1. Delete a large number of emails (many hundreds to thousands)
2. Click on any other email message.

OBSERVED RESULT
I get the "Retrieving folder contents" message

EXPECTED RESULT
I would expect to be able to view other email messages while the operation completes in the background.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 34
(available in About System)
KDE Plasma Version: 5.22.5
KDE Frameworks Version: 5.85.0
Qt Version: 5.15.2

ADDITIONAL INFORMATION