550 5.4.1 Recipient Address Rejected

Occasional Visitor

I have some o365 users who have had name changes. These accounts are now refusing to receive emails from ONPREM users with the following error “550 5.4.1 Recipient Address Rejected”. I have found these problematic users appear to have X500 address mis-matches which I can’t seem to resolve on the o365 side. Deleting the o365 mail account and allowing it to re-create fixes the problem.


Deleting the on-prem mail contact and re-creating from the o365 account doesn’t appear to work.


Just wondering if I am missing something really simple here, or if the only way to resolve these type of issues is to delete the o365 account and allow it to recreate?

1 Reply



I assume the users are synced from On-premise. It this is correct then you will need to look at the user's exchange attributes on-premise. The SMTP address would be stored in the users AD Attributes, so open the user up and see they have for proxyAddress. One thing would be to update the proxy address to include both the new and the old address. Then ADConnect replication will push the changes to AzureAD.