I love BuyVM. But they host almost everything (as long it's not illegal).

Being a neighbor to Tor exit nodes makes mail servers complicated.

You can use the blacklist check tool at https://mxtoolbox.com/SuperTool.aspx to check your IP's reputation.

Bad actors frequently use BuyVM's services, also known as FranTech and Ponynet. Their popularity with Tor operators probably doesn't help how their network traffic is perceived either. As a result, organizations may handle traffic from their ASNs unfavorably.

I don't have a personal opinion about the company; however, email is important enough that it's worth considering edge cases and future scenarios.