Microsoft is deploying a change to the Exchange Online transport server to allow tenants to set the message expiration timeout interval to between 12 and 24 hours. The default for the service remains at 24 hours. Reducing the interval means that users will learn about message failures sooner. The hope is that they’ll be able to respond to those failures and resend messages once they learn about problems.
Microsoft hopes to accelerate the removal of TLS 1.0 and 1.2 connections from Exchange Online by disabling connectivity in 2022 and forcing organizations which need to use the older protocols to connect to a new “legacy smtp” endpoint. It’s not a bad plan because it transfers responsibility for choosing to use obsolete connections to customers. Most organizations will go with the flow (no pun intended) and use TLS 1.2, but those who need some time to update applications and devices know what they have to do.