User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Firefox/91.0

Steps to reproduce:

1. Select Compact folders automatically when asked.

Actual results:

Aler box "Operation in progress" when compacting folders keeps poping up and taking focus. When clicked OK, new alert box pops up for other IMAP folder.

Expected results:

Compacting folders automatically should happen in the background. These alert boxes are just taking up focus, anoying and doing nothing usefull.

Confirming based on comment 0. I'd agree with reporter that Compact (especially when automatic) should be smart enough to not try compacting a folder who is currently blocked by another operation. The alert (if needed at all) should be inline instead of hijacking focus. Nothing really bad happens when compact fails, should retry automatically at a better time (if automatic). Notifying the user might still be good because his folder size may remain big, and messages thought deleted will still hang around, which is a privacy risk of sorts.

similar reports have been duped to bug 288896