Most efficient newsletter software

Hello everyone,

A friend of mine approached me with a request for a piece of software that would allow him to send newsletters and bulletins. He wants to send 1,000 people 15 newsletter per year and 10,000 people 10 newsletters per year. He suggested that I develop an ad hoc program for it. However, I think since that is a very commonplace use, there must be some cheap/free alternatives and is not worth developing an app for himself.

I’ve conducted a bit of research and I’m overwhelmed by the amount of programs I’ve found. Considering the volume that we are interested in, do you have any suggestions?

Thanks so much