Recipient: {0} Check the email address spelling, and run the checks again. If you used the intended recipient address, they're ...

Recipient: {0}
Check the email address spelling, and run the checks again.
If you used the intended recipient address, they're not receiving email because they don't exist in your email system. To fix this, you need to add them to Office 365 using the following steps.
  1. In the Office 365 Admin center, go to Active users.
  2. Choose Add a user (Add icon).
  3. Provide the requested information, and a mailbox is created automatically for the new user.