We can't speak to what the ICS department knows about email service provider requirements. We do know they have been in communication with them to reduce the sudden increase in failed email deliveries from Church domains and apps like Send a Message over the past couple of years. There are several topic threads on the Tech Forum discussing this. In October 2023 member Church accounts were updated to include opting out of a list of subscription services provided by email. One of those options is Local Leader Email (Email messages delivered using Church systems that were sent by your local leaders.). If I recall correctly my option was deselected when I first found out about the new options and checked it. That could account for members now just noticing they are not getting leader emails.
JD Lessley
Have you tried finding your answer on the ChurchofJesusChrist.org Help Center or Tech Wiki?