Issue
I am getting a tenant attribution error when sending specific mail: 550 5.7.64 TenantAttribution; Relay Access Denied
Error: 550 5.7.64 TenantAttribution; Relay Access Denied.
[DU6PEPF00009527.eurprd02.prod.outlook.com 2024-03-25T15:46:02.097Z08DC4B4F482A0112]). A non-delivery report (NDR) message was sent to zzz@yyy.com. The NDR might provide more details about why the email message wasn't delivered and how to fix the issue.
Reason
Microsoft have released a change to how mail is routed and the requirements surrounding this, specifically concerning inbound connectors. This staggard roll-out was scheduled to begin in November of 2023 but some Microsoft delays saw the changes not propagate until recently for most users. Please see the Microsoft article here. Microsoft are enhancing security around email and this change is a small improvement to how mail flow is handled by their exchange servers.
Please Note: This does not affect normal email and they will be processed as usual. However, it does affect a small subset of email in which there is a null sender, or the return path is not specified – for example: automatic Out of Office (OOF) replies.
What do I need to do
There are 2 ways to mitigate this issue. If neither of these solutions are workable for your organisation, please contact support@crossware365.com and we can discuss different resolution methods.
From Microsoft Exchange Admin Center > Navigate to Mail Flow > Create a New Rule > Define the conditions based on scenarios below:
A. Create a Transport Rule to bypass the Crossware Transport Rule on out-of-office replies.
B. If a signature is absolutely required on automatic OOF replies, a signature or disclaimer can be added at the exchange level. Create a Transport rule to exclude Signatures from the Crossware Transport Rule and instead, add a signature from Microsoft.