Currently Being ModeratedOct 25, 2011 3:48 PM (in response to Justin Bitner)
It's very unlikely that your account has been accessed or compromised.
What's almost certainly happened is your email address has been set as the sender address by some spammer. Nobody needs access to your account to do this. Anyone can do it simply by changing the sender email address in their email client. Soon enough the spammers will move onto someone else's email address and they'll get the bounce backs instead.
It's doubtful you have anything to worry about.
Currently Being ModeratedMay 26, 2012 2:16 AM (in response to Justin Bitner)
When that happened to me, my ISP (internet service provider) simply added a password to my email settings, such that any email sent out under my address has to have the password. This works quietly in the background because the password is automatic when *I* send email, but when spammers attempt to send, using my address, they can't because they don't have the password.
I THINK I understand this correctly (check with your own ISP). But MAYBE this was set up using the settings in Apple mail (you can research it further, or maybe someone will come on here with more specifics). In any case, the problem I once experienced frequently has disappeared completely.