550 5.7.64 TenantAttribution; Relay Access Denied
Posted by Sinclair Hughes, Last modified by Sinclair Hughes on 22 July 2019 12:43 PM

Sending emails through Office365 sometimes causes message send failure with an error of 550 5.7.64 TenantAttribution; Relay Access Denied.

  1. In Office Admin go to Exchange
  2. In 'Mail Flow' go to  Connectors
  3. Use the wizard to complete the Connector process.

Make sure the external IP is recorded as an allowed address on the Inbound Connector in Office 365:











Also, add the IP address to the SPF record in Public DNS like this:

v=spf1 ip4:, include:spf.protection.outlook.com ~all

One other possible cause of this issue is if the application, when it composes the email, uses a domain other than what is on the accepted domains list. For example, if your tenant has 3 defined domains – BobsGarage.Com, TimsGarage.Com andJohnsGarage.Com and the application sending the email uses a domain like GaragePower.Com, then the connector in Office 365 will reject the email. If you receive the relay error, here is the order I would take for troubleshooting:

  • Verify Sender address is using an accepted Domain (in the application, or message header)
  • Send the email to an internal recipient – check headers for IPs to match in the connector
  • Check your SPF record to make sure all IP addresses are listed as well