How do we send bulk promotional email without using 3rd party services (ClickDimensions)?

Goal is to send 5K-10K/day bulk promotional cold emails campaigns directly from online Miscrosoft CRM 2016 to a remote SMTP server.

We have been told Microsoft CRM SMTP integration tool works only for Gmail.

So we are told to setup email router to connect to a SMTP relay.

Any suggestions on setting up email router?

Who provides 3rd party SMTP relay service?

Any better ideas? 

Thanks