Choose the server account used by your email account.

(or similar) from the bottom of the pop-up menu

Find the “Outgoing Mail Server (SMTP)” field and click it to get a pop-up menu.

Next, you need to change the password in the outgoing mail server settings: Erase the current value in the password field, then carefully type in your new password.

Make sure the Account Information tab is selected at the top of the main area of the window.

Select your email account in the list on the left-hand side of the window.Make sure Accounts is selected along the top of the “Accounts” window.Open the Mail menu and choose Preferences.To update an old version of the Mail app with your new email password: Older versions have the second password in a different location. If you’re using an older version of Apple Mail, such as the version included with Mac OS X “El Capitan” or “Yosemite” Although it doesn’t seem that it should be necessary, we've seen several cases where the Mail program keeps sending the wrong password until you actually quit and re-open it.

Cannot open apple mail preferences