InvalidOutgoingMailboxEmailAddress error appears in Dynamics 365 mailbox alert

When you click Test & Enable Mailbox on a mailbox record in Dynamics 365, the test results are not success. Additionally one of the following alerts appears within the Alerts section of the mailbox:

• "Email can't be sent for the mailbox [Mailbox Name] because the mailbox record doesn't have a valid email address. The mailbox didn't synchronize. A notification about this is posted on the alerts wall for the owner of the email server profile Microsoft Exchange Online.
  
  Email Server Error Code: InvalidOutgoingMailboxEmailAddress"
   
• "Email can't be received for the mailbox [Mailbox Name] because the mailbox record doesn't have a valid email address. The mailbox didn't synchronize. A notification about this is posted on the alerts wall for the owner of the email server profile Microsoft Exchange Online.
  
  Email Server Error Code: InvalidIncomingMailboxEmailAddress"

This error occurs if there is not a valid email address in the Email Address field of the mailbox record.

1. Correct the value in the Email Address field and then click Save.
2. Click the Test & Enable Mailbox button again.
3. If the test results are not success, view the message and help link in the Alerts tab.