Well, first they tell us that Basic authentication won't be disabled when you announced the deprecation of BA, as NateL1010 reminded you of, but a few months later MS is still deprecating it.
Now we're facing two problems.
First: External companies that were allowed to send from our domains with Authenticated submit accounts. That way everything was authenticated and logged what was send from that company in our names. We'll see if we can implement Azure Communication Services Email for that functionality, not yet familiar with that.
But another big issue is all our multifunctional printers who deliver their scans with email to the user who scans a document.
As jc98jc correctly mentions, MFP manufacturers are not the quickest in updating this, as if this is going to be adjusted at all! Direct send is killed this way.
In my opinion the only way to keep using them is to place an Hybrid server (or other SMTP relay) with anonymous access and relay that mail through that server?
Correct me if I'm wrong.