Mass mailing server software

I use an advanced webmail service every day but now I need a simpler tool but for a larger number of emails (database between 1 and 3 million records). Certainly, it is necessary to change the domain from which emails are sent, determining the gap between emails in milliseconds. The matter of editing the text to be determined. Returns management (reflected, cannot be delivered etc.).

I am waiting for suggestions from people who know the subject of mailing