I've also been happy with mxroute.com which has super low cost promos every November (black friday) so I'm on a $15/year plan. Regular pricing starts at $45/year for unlimited domains and mailboxes, 10GB storage.
The killer features are unlimited mailboxes and per-mailbox quotas. I make a new mailbox for every device and give them a quota that makes sense; 10 messages per day for most. If a device goes haywire, gets compromised, or gets stolen, it’s one mailbox to fix and maxes out at a super low quota, so it’s useless for spamming.
That’s 100x better than the options on Office 365 which absolutely sucks ($$$) for low volume email coming from devices.