On Mac Mail 3.6 [(OSX v10.5.8 - Leopard) + (hawaii.rr.com Road Runner account)] I receive only two mails then the program gets stuck. I need to (1) go into Road Runner's web mail site and delete the two mails that came in, (2) force quit Mail, then (3) restart the Mail Program. This keeps repeating, two mails at a time. I just inherited this Mac from a co-worker who was having the same problem on his own account.
Also, I'm not sure if this is related but I tried importing some messages/mailboxes from my old computer mail. The mailbox and message hierarchy was intact but some of the messages had no content at all, just blank.
And after moving the old mailboxes out of the transfer folder, some messages cannot be deleted.