Please see Update on Transport Enforcement System in Exchange Online for an updated timeline.
2/20/2025: Please note that thottling/blocking has now been enabled for all versions of Exchange Server...
Updated Feb 20, 2025
Version 8.0
Blog Post
10 MIN READ
Throttling and Blocking Email from Persistently Vulnerable Exchange Servers to Exchange Online
Hi,
In terms of:
- the extended support of Exchange Online 2019 that ends next year in October 2025
- using Hybrid Exchange for SMTP Relay from multifunctional devices (even sending with TLS 1.0, 1.1)
Will sending email from Exchange Server 2019 to Exchange Online in a hybrid environment by SMTP Relay be blocked from October 2025? Or does Microsoft have other plans for allowing Exchange Server 2019 send email to Exchange Online in a hybrid environment next year?
The answers for these questions will be helpful for planning what actions we should have for Exchange Server 2019 next year, and also the needs of migrating any SMTP Relay dependencies from the Hybrid Environment, to the cloud.