How to resolve 'com.apple.accounts error 3' when adding an Exchange account in Mail?

vadis5150 wrote:

When trying to add an Exchange account to Mail I receive this error: The operation couldn’t be completed. (com.apple.accounts error 3.)

I entered my exchange email address, password, and multi-factor authentication code. Then, this error message appears.

[Re-Titled by Moderator]

Original Title: com.apple.accounts error 3

Common issue is if you have VPN enabled, if so disable or delete it.