I have been having a Mail problem. Not really it is more of a keychain access problem. For what ever reason when I have Mail open over time I get a warning saying that my POP server has rejected my user password which I have to keep filling in. What I think is happening is keychain access is sending the wrong password. I am not sure what is causing it but I have a feeling it is a recent version of Seamonkey I downloaded. Things seemed to start happening after that. Or at least my keychain access started going strange after that.
A preference had been changed for POP mail accounts. Under the Advanced tab at the bottom there is an Authentication drop down menu where the setting was changed to "authenticate POP". It needs to be "password".
Since changing this setting I have had no more problem.