Mail forgets all my passwords. 10.8.4.
I have about 10 different domains, all on different servers, on different hosts, with various accounts linked to Mail. Some are IMAP, some are POP3.
Mail forgets the password to each and every one of them on a periodical basis. Sometimes it's every week, sometimes I go a month, but then it forgets.
I then have to dig out my password store and paste in all the passwords again. I typically have to paste them in, then have mail complain that it still can't connect, paste them in a second time, and then it's works and mails send and receive again for that domain.
Mail then complains about the next domain, and I have to dig out the password for that.
And then Mail still complains about not knowing the password to things like my icloud and gmail accounts.
MacBook Air, OS X Mountain Lion (10.8.1)