Actually it's usually just accounts the spammer signed up for that purpose. It's so easy to get an account that there's no point bothering to steal credentials.

98% of email is keeping a clean IP range. Getting a clean IP is good for maybe a week if you don't know how to keep it that way.

What does it use on the back end for the mail delivery?

Thanks!

Hi All, for years Open Source MTA technology has lagged behind the commercial options for high-volume sending, we're here to change that, check it out!

Hey all, we're a group of email infrastructure industry veterans, and before that were contributors to PHP and MySQL, and we decided that it was time for there to be an Open-Source MTA as scalable and flexible as the commercial options, and so KumoMTA was born.

We just cut our first production release and hope you can give it a try, it's great for all forms of email sending, but excels in high-volume, multi-tenant environments.

Announcement is linked to in the post, repo is at https://kumomta.com/repo