Updated Requirements for SMTP Relay through Exchange Online

Faber Paul Robinson 

The following are ways to verify whether the upcoming change will impact your organization.

1. Send an email from the path (whether it’s app in IIS, scanner, etc.) to yourself. Check the email header (View internet message headers in Outlook - Microsoft Support). If property value of “Return-Path:” contains a domain name that does not below to your organization, but domain in property value “From:” or “sender:” belongs to your organization, then you will be impacted.
2. From Message trace, get “Extended report”( Message trace in the modern EAC in Exchange Online | Microsoft Learn). If you find traces that match all conditions listed below, then the change will impact you.
1. The “directionality” is “Originating”.
2. In “custom_data”, there are property “S:InboundConnectorData=Name=xyz;ConnectorType=OnPremises;”, where “xyz” is the name of the inbound connector name.
3. The domain in “return_path” does not belong to your organization, but domain in “sender_address” does.