Sometimes, your end users might receive a Status 403: Office 365 returned us an email address different from the one that started the authentication process. error message when they try to authenticate with Microsoft 365. This usually happens because the end user tried to authenticate using two different email accounts in the same flow.
You should work with your end user to…
- Make sure they’re entering or selecting the same email address on both Microsoft 365 and Nylas.
- Make sure they’re not attempting to log in to an alias. They must authenticate using their main email account.
If the issue persists, ask the end user to log out of all their Microsoft 365 accounts (or open an Incognito or Private browser session), then try to authenticate with Nylas.