On Linux, I had a couple of encrypted partitions
On the Mac, I think FileVault offers the same sort of functionality, but it doesn't seem to have a very good reputation. A very small amount of poking about on the net will find users with horror stories.
Then my Mac crashed. Game over. Power cycle, please.
When it came back, a not large, but non-trivial hunk of my mail archive was corrupted. Not only did it take a while to get things back into a state where Gnus would even show me the mail, after it would, it became clear that some tens of messages in some tens of folders are now random encrypted junk.
There are a few ways to recover from my mail backups, but none of them are pretty. I might just assume those missing messages weren't important. And I might go back to storing my mail without encryption.
Right now, I'm probably too mad to make a rational decision.
[Update: …several hours pass… I just couldn't stand it. I had to go back and recover from my backups. What a PITA. I may have lost some of my replies, but that's the best I can do, I think. Now I just have to delete all the spam again. And I'm not encrypting my mail anymore, at least not this afternoon. What's left of it.]