Sending emails through Office365 sometimes causes message send failure with an error of 550 5.7.64 TenantAttribution; Relay Access Denied.
- In Office Admin go to Exchange
- In 'Mail Flow' go to Connectors
![](http://incisivesupport.com/support/__swift/files/15637559852069d9bdedb8aca21185df4a7fff1dad709fd17f.png)
- Use the wizard to complete the Connector process.
![](http://incisivesupport.com/support/__swift/files/1563756141ae5279a75b24a3efd17e13ba5b461372f1f7e3a7.png)
Make sure the external IP is recorded as an allowed address on the Inbound Connector in Office 365:
![InboundConnector2](https://justaucguy.files.wordpress.com/2015/05/inboundconnector2.jpg?w=300&h=179)
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
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