Recently, I did some trial use on the following VPS.
I am still seeking a better VPS for Email servers and web hosting.
One of the new VPS providers is Hetzner. I test a server and found it is more powerful than Contabo. The only thing I don’t expect is that Hetzner blocks port 25 for email server in general. I have to wait one more month to see if they will open the port to me.