Email address not found

Question

We've recently got 365 for our charity and email addresses through this which match the domain name of our charity. I can open the email account in Outlook, however, when testing this emails to the new address bounce back saying
"Address not found. Your message wasn't delivered to XXXXXXXXXX because the address couldn't be found or is unable to receive email."

Have we skipped a step in the set up? Any ideas gratefully received.

Answer 1

Hi @Lindsey ,

Welcome!

According to your description, sounds like you have an O365 email account and have already successfully configured to your Outlook desktop client, but encountered errors when sending or receiving email messages, right?

If yes, when testing this emails to the new address
What tests are you exactly operating here? using this email address to send messages to other users? Or using this email address to receive messages from other users?
And does this issue only happen when sending or receiving from specific users? What if you try some other users?

In order to confirm if your issue is related to your Outlook desktop client, it is suggested to do the same send/receive tests on your web mail and see if the issue has any difference there.

By the way, I tried some search about your issue and found some related information, please check if it could help:
Fix email delivery issues for error code 550 5.1.1 through 5.1.20 in Exchange Online

If you have any update about this issue, please feel free to post back.

---

If an Answer is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.