"Delivery has failed to these recipients or groups" when sending emails in FYI

Issue

I can send emails directly from Outlook but when sending an email from within FYI I am getting the following error:

• "Delivery has failed to these recipients or groups: email address. Your message wasn't delivered because the recipient's email provider rejected it."

Cause

This error can happen when you are trying out Microsoft 365 trial.

Solution

If you receive this error, before you can purchase licenses, you will need to purchase a full Microsoft 365 license.

Refer also to the following Microsoft article NDR error codes 550 5.7.703, 550 5.7.705, 550 5.7.708, and 550 5.7.750