If after witnessing a Rackspace meltdown someone is still a glutton for guaranteed pain and wants to go down with the Hosted Exchange ship, Intermedia has been around doing it for a long time.

Otherwise, SMEs should find a good value-add licensing partner and move to O365. Use a proper migration service to make it easy.

If you're open to non O365 things, then potentially something like OX Cloud:

https://www.open-xchange.com/products/ox-app-suite/

I haven't used them though, just became aware of them a few years ago when they picked up PowerDNS (an OSS project I used to help out a little bit).