I have worked in this area for a long time, and it's very rare that this causes any problems unless you are a spammer (or "news-letter sender"). You won't end u

I have worked in this area for a long time, and it's very rare that this causes any problems unless you are a spammer (or "news-letter sender"). You won't end up on black lists unless there is a mistake. It's an annoyance when that happens, but that happens for the major players as well. I often feel the ambivalence to your own mail servers is unfounded. A basic apt-get for Postfix and Dovecot will give you secure defaults. The only thing you need to do then is to set up the certificates, the dns records, and keep up with what happens in the future. It's absolutely comparable to running your own web server, where you also need to change a cert or two over time.