Update 11/13/2023: We added new information on how to know when this change is released to your organization.
Today, we are announcing an update to our requirements for SMTP relay through Exchange ...
Updated Feb 22, 2024
Version 19.0
Blog Post
Carolyn_Liu
Microsoft
MicrosoftUnfortunately, this change is at the system level, not at tenant level, therefore it is unable to report at tenant level that the change has been applied. We do plan to inform everyone, when deployment completed, and for sure it won't finish by EOY, and we aim at Q1 2024.
When the change does get deployed to your org, and from the previous extended report you do see your organization were impacted, then you should see one of the SMTP errors below:
- "550 5.7.64 TenantAttribution; Relay Access Denied."
- "451 4.4.62 Mail sent to the wrong Office 365 region. ATTR35."
- "451 4.4.4 Mail received as unauthenticated, incoming to a recipient domain configured in a hosted tenant which has no mail-enabled subscriptions. ATTR5."
- Email rejected with "452 4.5.3 Different recipient domain on a smart-hosted and non-authenticated email. Sending server should retry this recipient separately next."
in addition, for the 1st error, the client should get an NDR, and for the rest errors mails from your on-premises environment would be queued.