All versions of Exchange Server (2016, 2019, Subscription Edition - SE) are now in scope for throttling / blocking of email by Exchange Online if servers are significantly out of date.
The minimum ...
Updated Nov 10, 2026
Version 7.0
Blog Post
Just to confirm, this timeline is only for M365 tenants with an inbound connector to an on-premise with an outdated version of Exchange (i.e. within an organisation)? This timeline isn't for external organisations with outdated versions that send to a M365 tenant?