Q: Rejected Password (Mail)

I was getting same issue a few weeks ago and semi-solved it myself in another thread

Looking at http://support.apple.com/kb/TS4002

 

My 10.7 Mail SMTP was on P02.-imap.mail.me.com (but this was grayed out so I couldn't try dropping of the P02).

found under the Advanced tab that my authentication had changed from Password to something else. Changed it back to password and Mail is now working on the Macbook.

However, I just started getting it again. Strangely, saw a different post that suggested changing the password authentication to Apple Token. I did this and issue has gone away. I think it was on Apple Token the first time this happened. So try changing the password authentication to either Password or Apple Token depending on what it is now.

Laz

edit - btw, my password works fine on iPhone, iPad, webmail so I have not tried to change it.

Follow the links in this thread.  Fixed the issue for me.

https://discussions.apple.com/thread/3888192?tstart=0