Getting off the hybrid-exchange clusterfuck train

Situation:

Hybridized Exchange environment (Exchange server 2016). All mailboxes have been moved to the cloud, no (important) public folders, The server isn't really doing anything except:

* Handling emails from our Xerox devices (scan to email)
* Handling some emails that get generated by an SQL server

Both of these use an IP Address based connector and relay the email through our 365 environment.

I have many issues with this setup, but chief amongst them is that Exchange 2016 and 2019 are hitting EOL next fall, and while a replacement Exchange product is "promised" it's not even scheduled to drop until next summer???, a whole several months before the current product goes EOL.

Maintaining a whole server just to relay email from my fucking copiers seems dumb. That said, as far as I can tell:

* Xerox devices still don't handle oauth /modern authorization.
* Although the documentation is immense and varied, Microsoft still maybe seems to discourage you from getting rid of the last exchange server?

We can't be the only org in this predicament. For y'all that got out -- how did you kill the last server and deal with devices/app that don't support oauth?

Edit for future travelers who end up here:

smtp2go got several mentions and that's what we went with. We've been super happy in our initial testing. We considered handling our own non-exchange relay server, but decided against it or a variety of reasons.

Regarding identity issues we've built a new (much slimmer) 2019 exchange server, added it to the environment, will be completely removing the old Exchange 2016 server, and then powering off the 2019 at some point in the future.