I wish "backing up" was really feasible for me, I really do. But can you imagine how expensive it would be to do that for 4TB of data?
Yes, there is. Do backups of the mail folder and, when a more serious issue happens, just use the backup to recover most of your data or even your entire data depending on how often the backups are done.
This is also not a fix for my current problem.
But why this is happening? You need to try to find the cause of the issue or it will continue to happen.
It's only ever happened following a crash, which there is no "explanation" for. But it's literally brought my ability to use the internet to a standstill every time it's happened. And it shouldn't be happening to begin with.
But then again, the fact that Opera has stopped development was a devastating blow to my productivity to begin with, one that I still haven't really fully recovered from. Thankfully I just discovered Vivaldi, and as soon as that gets on stable footing, I'll be making that switch, hopefully for life.