I am afraid that I need to step in and correct @kellytrinh’s comments.
ALL VPS providers have the ability to see what you are running on their services. ALL.
The question is … how much do you trust the VPS provider to not look?
Now, in general, they have no reason to look nor will they under normal circumstances HOWEVER should they get a complaint, you can bet your last dollar that they are looking.
At one time, I had a client who owned a rather controversial domain and I hosted email for that domain using MiaB. DO received a frivolous complaint directed toward that domain and stated that they did not want that domain using their services. So I was off to find a different provider. The next provider that I found ALSO requested that the domain be removed from their services as they used grep to discover the domain’s email was being hosted on their VPS. There was none of the domain’s content present on the mail server, simply the signature file which included the domain’s URL.
Moral of this story … any and every VPS provider can peek. IF you require absolute privacy, you need to host a mail server in your basement where only YOU have access. The problem is that email does not work very well when hosted in a residential setting for all the reasons you can discover elsewhere on this forum.
@wyzard also let me answer your questions that you presented to Kelly if I may to give you another perspective.
I’ve been using MiaB for going on 4 years now. I am very happy with it though there are some minor features that I wish it had like quota management and SSO. It is absolutely more private than Gmail as there is nobody actively scanning your email for marketing data which Goofle/Gmail is well known to do. I use a variety of VPS’s from several providers around the world. Digital Ocean is NOT one of them.