Best service for simple low volume email marketing?

I need a service to send out emails to customers. B2B, no customization needed, just need to send current offers to my list of around 100 people.

I've tried mailchimp and constantcontact so far, but both banned me before I could send out a single email, and refused to give out any information. They didn't say I did anything wrong, just that they refuse to do business with me. At first Constant Contact claimed I was banned because I used a VPN while signing up and suggested I create a new account, but the new account was also banned by what I was told was the Compliance team.

Everyone on my list opted in, this is not spammy content, so I don't understand why nobody wants to do business with me.

Is there a simple service that doesn't have any of this nonsense?