As expected, something went wrong. I had a vague sense of intuition that it would be my mailserver... and it was. I reinstalled postfix and everything is working. I was reinstalling courier-imap when it complained about libintl.so.4. I hate that file SO MUCH. It always shows up. Stupid shared lib. It comes from gettext, and so I tried reinstalling gettext and got the dumbest error message in the world ever:
-r: not found
Now what the hell does that mean? Absolutely NOTHING. Anyway, so I abandoned that because as I discovered, the old version of courier-imap was working perfectly.