Briar and SimpleX seemed decent the last time I looked into this.
I ended up using neither because I don’t need privacy when talking to myself.
I can recommend Kagi. Happy customer for over a year.
Some reading to get started:
I’ve used EasyOptOuts for a few years. The only one I can recommend. They do the work and are cheap.
Got it. So more for data at rest rather than handling the sending too?
SimpleX does file transfer pretty well, not sure about Briar now that I think about it.