Mail can't connect to... non-existing account I get alerts from mail that a password to one of the mail accounts is not valid. This may well be - however, I'm not using that account any longer. In the account list - this account is NOT present - so I couldn't remove it. 




I think mail is either confused somehow because this old account has been replaced by a similar account (anne@mydomain.com is now anne.stahl@mydomain.com). Or, perhaps the old account is still on one of my other devices (iPhone or iPad) and somehow saved in the cloud (I checked the devices).
After trying all sorts of things with Keychain and other devices I finally figured out what is causing this. The offending 'account' was in the SMTP list. You can find this by going to 'Preferences' in the Mail app, select the 'Accounts' tab, click on the dropdown for 'Outgoing Mail Server' and there you can 'Edit SMTP Server list'.