MAIL won't stop asking for a password.

In Mail's Window Menu, choose Connection Doctor, any red dots for status, if so what is the exact message?

Then click the Show Details button & Check again.

The Password rejection can confuse people since it's a catch all meaning...

This Password, Username, Authentication method... is not recognized on this Port to this Server.

So if WebMail works it's not Name or Password, but one of the other ones.

Could be this?

Keychain Access asks for keychain "login" after changing login password...

http://support.apple.com/kb/HT1631

If using a browser to login via WebMail works with the same info, it's not Name or Password, but something else.

I've had this problem too, and it's always because the password for the POP3 account gets deleted from Mail's Preferences (under Accounts), or else a duplicate keychain entry has somehow appeared--without a password--and that's the one that Mail chose when it was time to fetch the mail. Have you verified that: (a) the password for this account is in the Account Information pane of Mail's Account preferences, (b) Password authentication is selected under the Advanced pane of Mail's Account preferences (with the port that your ISP has recommended and also the Use SSL checkbox if applicable)?

Also, check Keychain Access for anything that looks like a duplicate entry for this account that doesn't have a password--for this you'll need to click the "i" button when the account is highlighted and then click "Show Password" in the popup window.

Who is your eMail provider, the part after the @ sign?

The Password rejection can confuse people since it's a catch all meaning...

This Password, Username, Authentication method... is not recognized on this Port to this Server, or a server end problem.

If using a browser to login via WebMail works it's not Name or Password, but one of the other ones.

The receiving email ports are:

IMAP is port 143

IMAP-SSL is port 993

POP is port 110

POP-SSL is port 995

Outgoing ports are...

SMTP and SMTP-SSL is on ports 25, 587 and 465. Port 587 has to be SSL, and port 465 is enforced TLS-wrapped and is generally used by Outlook users.

I have been plagued by the same problem for months. Just tried something which seems to have fixed it; no idea if it will work for you. Under Preferences > General, I found that my Default Email Reader said "Eudora", which I used as my mail client years ago. I set it back to Mail, and the password requests seem to have stopped.

Could be wrong, but thought I'd share.

This happens to me too, incessantly!! The worst thing is I can be typing in another window and suddenly I'm typing in the password bar that aggresively pops up again and again - driving me so nuts! At the very least, the password request could remain in the background. Alternatively it would be good if I could limit the number of times Mail prompts for a password per hour.