The Reply-all Storm Protection feature in Exchange Online helps protect your organization from unwanted and disruptive reply-all storms. Last year we updated the feature to give admins the ability to...
Updated Apr 23, 2022
Version 2.0
Blog Post
KevinShaughnessy
Microsoft
Microsofttonire , MisterKevin is on to something here wrt to SRS and relay pool (#3 in the SRS blog post). At the end of last week the relay pool was fully enabled world wide and the likely reason for not doing the SRS rewrite is due to the message identified as subject to being routed out via the relay pool. As noted here: Outbound delivery pools - Office 365 | Microsoft Docs
The forwarded or relayed message should meet one of the following criteria to avoid using the relay pool:
- The outbound sender is in an accepted domain.
- SPF passes when the message comes to Microsoft 365.
- DKIM on the sender domain passes when the message comes to Microsoft 365.
The support engineer handling your support ticket should be able to assist you to configure your scenario properly to avoid getting tagged for sending out via the relay pool.