To make sure this doesn't happen again, update your mail flow rules. In the Exchange admin center, go to the Rules page. ...


To make sure this doesn't happen again, update your mail flow rules.
  1. In the Exchange admin center, go to the Rules page.
  2. Choose the rule that rejected the email, and do one of the following:
  • Choose Edit to customize the rule to fit your needs.
  • Choose Delete to remove the rule entirely.