Question on Email Password

Lately I've been getting queried for my email password even though I always check the box to keep it on my keychain. Is there a permanent method to store a password that I'm missing?

what king of email address are you using? my setup was my email address on my macbook and on the imac. the wifes email address on her macbook and on the same imac. when the imac had mail open and i opened mail on the imac, it sometimes asked for the password.

I have two (2) comcast email addresses on this machine. That's it other than the occasional gmail, and while I have dot mac setup, I don't really use that email.