Mac mail and exchange server 2003 problem

I just tried that and Thunderbird seems to be working with no problem. So I think that client is doing something weird.

Did anything change on the server side?

There have been no server updates or anything else that we can figure out that could have changed that might cause this. We set the server to never let my password expire, but it is still locking me out after the 3 attempts to connect. Mail is configured to check every 5 min. So I am having to use thunderbird until I can find a solution.

Did you pick a longer password than usual? And rather than resetting your keychains, delete the prefs to them (even the system level one).

I had similar problems, although not with an exchange server. The problem had nothing to do with my password -- it was just that if my internet connection was ever slow (because my cable internet was slow, because I was up- or down-loading something large, because I was sending mail with an attachment, because I was Skyping, because the planets aligned the wrong way) then I got a password-incorrect error. Apparently MacMail is just really touchy about speed, and if something slows down its access to the server, it assumes the password must be wrong. I discovered that when I got this password-incorrect error I could just hit Cancel, and then hit Get Mail (and I'd have to tell Mail I was online again) and all would be well again. It's not a permanent fix, and it might not apply to you, but it's something to look into -- see if you get this problem when something is slowing down your connection, and if cancelling the error box works, so that you're not sending multiple password attempts. Capri

Is your account setup as IMAP or Exchange in Mail.app? I would check the password type you are using, in Preferences -> Accounts -> Advanced tab, usually you will see something like password or md5 challenge response. Try a different one, check to make sure you are using the right ports if using imap, 143 for non encrypted and hopefully 993 for SSL encrypted. I believe the Exchange support uses 993/143 and also 80 or 443 for the webdav / outlook web access scraping. That is where I would start.