how to find password for email account in Mail

In safari preferences > passwords > enter your admin password in the opening window click on the mail account you can read the password .

It can be viewed in keychain access see this article View the information stored in a keychain on Mac - Apple Support , but deleting the password from keychain access ( it will be shown in iCloud is risky ) it can corrupt the keychain .

It is always wiser to change the password from web account if it is an gmail account see this article Change or reset your password - Google Account Help

You are welcome. Who is the e-mail provider? What is the error message you are getting? Delete the password from Keychain Access (Applications/Utilities). One option is to delete the account and set it up again in Mail/Preferences/Accounts.

For an iCloud e-mail account, it should be your Apple ID password.

For other e-mail accounts, go to the e-mail provider's web site, enter the e-mail address and click the Forgot password option.