For about the past two months, I have been unable to access .Mac's webmail page. Whenever I would try to login, I'd get a message saying "Sorry, the service is not available, please try again later." It didn't matter if I was at home or at work, using the G5 or the PowerBook -- I couldn't get into webmail, but all other .Mac services worked, as did other Apple services that use the same login ID.
When the problem first started, I wrote to .Mac support, and we had been having an ongoing dialog in attempts to repair the problem. They had me create a new user and enter my existing account info; no go. Then they had me create a new .Mac trial account, and that worked fine (in both my primary and new users). But my existing ID still didn't work.
Today, .Mac support wrote back with one astoundingly simple suggestion that I had never thought to try -- resetting my .Mac password. Duh! Once I had done that through the main .Mac account page, webmail was instantly functional again. Somehow, the webmail portion of .Mac thought I was giving it an incorrect password, even though I could use my iDisk, login to the Developer site, and update my .Mac homepage. So if you're having trouble with webmail, try a quick password reset.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040819070704486