Your password is administered with your email provider. Since you foolishly posted your email address in a public forum it looks like that is Comcast.

Go to their web mail or email help page and look for a link to reset your email password/

I entered my old password and the message came up as incorrect. Now I don't know how to solve this new problem....

If you go to the comcast.net site can you log into your account there. This will confirm that your password and username are correct. If not fix the password while there.

Incorrect server settings or an overactive antivirus software can also cause password problems.

You can post your troubleshooting info here and have your server settings checked. You do this from the Help menu. Select Troubleshooting Information. Clear the check box to include account names. Press Copy all to Clipboard and then come back here an paste that info into the reply window.

It could also be that your provider is having a problem. I am also a Comcast customer and this happens to me once in a while. I usually try again a little later and it works fine.