I've been running my own mail server off of a residential connection since 1998, so... 18 years. I do pay for a static IP, and I switched ISPs away from Comcast (who had inherited me as a customer) when they abruptly started to filter inbound port 25 and claimed I had a malware infestation.
For years it was qmail, but when I wanted to use SMTP/SSL as much as possible, switching to Postfix was easier than maintaining all the qmail patches.
I switched over to Let's Encrypt certs several months ago, and those have been working out quite well for me.
FYI they don't filter inbound OR outbound port 25 if you're a Comcast Business customer; in fact I think the only ports they filter for business customers are a couple of ports only used for remote attacks on MS Windows boxes.
You know how Comcast gets the Worst Company in America award every year or two? I really don't feel any desire to go back to them.
As far as I can tell Comcast employs a number of very competent network engineers and an astounding number of horrendous customer service and executive managers.
I don't understand. Many providers block the outbound 25 port because of their distrust of the infected computers of their end losers. What could possibly be their rationale for blocking the inbound 25 port?
A lot of ISPs say you are not allowed to run 'servers' on your home internet, and hence block inbound low ports like SMTP, IMAP, http. It's just extortion.
Incompetence. At least that was the reason why my ISP at the time blocked both outbound and inbound port 25. It took a couple of weeks to convince them that they where wrong and open for inbound again.
For years it was qmail, but when I wanted to use SMTP/SSL as much as possible, switching to Postfix was easier than maintaining all the qmail patches.
I switched over to Let's Encrypt certs several months ago, and those have been working out quite well for me.