Change password for Comcast Mail on the Mac

Mail > Preferences > Accounts ...

... will show you a list of Accounts and their main setups. Select the account that has changed and enter the new information. This is preferable because it will often fix BOTH sender and receiver in one go. -OR-

Mail > Window > Connection Doctor ...

... will show you a display with red and green lights for each Server (sending and receiving). Double-click any red light to go directly to that Server and enter the new information.

Some email providers do not place a high priority on their Servers being available 24/7. Many operators freely take their mail servers offline for backups and service without notifying or compensating you.

Mac Mail has only one thing it can do when a mail server does not respond. That is the same thing it does 3 seconds after initial setup. It asks you to try re-enterinig your password again. Almost always, this is not helpful. In some cases, it destroys your perfectly valid password and leaves you with NONE.

If your mail has been running for a while, and you know the password has been good, just dismiss the box asking for the password and try again later. When the Mail Server is back up and running, it will connect just fine.

For increased Visibility, use:

Mail > Window > Connection Doctor ...

... to get a one-page display of the status of each sending or receiving Server. Sometimes you will see status that tells you more about what is really going on.