Messages automatically
erased from
Junk according to your settings don’t go anywhere. What would be the point of moving them to the Trash? Mail is just doing what you’ve told it to do, i.e. erase the messages after the specified amount of time.
There is a small chance that the messages haven't actually been erased, though.
For each mailbox, Mail 1.x stores messages sequentially in an
mbox file within the
*.mbox package associated with the mailbox -- you can see the files contained in an
*.mbox package by ctrl-cliking on it in the Finder and choosing
Show Package Contents from the contextual menu that appears.
When a message is removed from a mailbox in Mail 1.x, the actual message may be completely erased from the
mbox file (in which case it cannot be recovered), or it may remain there just marked for deletion in one of the other supporting files within the
*.mbox package.
In Mail, do
File > Import Mailboxes. I’m not sure what the import options available in Mail 1.3 are, but you should choose
Other / Standard mbox, or something like that. Follow the instructions to import the
Junk.mbox package that’s within the
~/Library/Mail/POP-username@mailserver/ account folder.
Importing as
Other / Standard mbox causes Mail to look at the
mbox file only, ignoring the supporting files that keep track of which messages are read/unread, marked for deletion, etc., thus causing any previously deleted messages that might remain there to reappear.