Office365 Recipient address rejected: Access denied

Funny thing happend……

For some reason new email accounts (older then 24 hours) and email aliases was not working properly within Office365.

External contacts was reporting:

tried to deliver your message, but it was rejected by the server for the recipient domain mydomain by

550 5.4.1 [<username>@<mydomain>]: Recipient address rejected: Access denied


  • Accounts was is getting propagated in an accepted time frame (24 hours)


  • ¬†The affected accounts is unable to receive email from external contacts – emails are not getting delivered.


  • We changed the accepted domain to Internal relay to resolve the issue.
  • As a precaution we enabled Conditional Sender ID and NDR backscatter to avoid spam attacks.

Articles on Mail Flow for reference:

Exchange Online Protection Limits

How Office 365 does SPF checks for customer-to-customer mail

Manage Transport Rules

Transport rules

Configure your spam filter policies

Submitting spam and non-spam messages to Microsoft for analysis

Advanced spam filtering options

Spam email and Office 365 environment

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