I'm slightly bothered by the fact that their servers are located in the worlds surveillance hotspots no. 2 and 3. but i guess email always has at least 2 involved parties, so it's not exactly "top secret".
I used to run my own mail server for years but spam was becomming a problem as it always does when running your own system and I thought the pricing of most of the services was poor if you had lots of addresses but didn't send/receive many emails. Spam hasn't been an issue for me with mxroute so far and their infrastructure seems to be pretty solid.
If you are the only actual user of those emails accounts, then it's a great option (I have 5+ domains under a single account with them)
I'm always very nervous when it comes to running docker in production. Also, it looks like it (by default) stores emails in a docker container, which in my book is just overcomplicating things. While i don't mind software being containerized, i much prefer having my data stored in the plain old filesystem.
AND they can import your gmail account. They imported mine in a few hours, 4.5gb of mails.
I'm planning on, once again, spinning up my own mailserver on a $5/mo VPS. Have lots of domains, but not that many users/traffic.