Yeah, a lot of people who run their own email server keep it for inbound mail, and use something like Amazon SES or Sendgrid for outbound mail (so it isn’t marked as spam). Most residential ISPs block SMTP’s port 25 as well.
You can often tell which ISPs are competently managed by looking at which direction TCP/25 is blocked. Around me, there are 2 ISPs.The one that I use blocks port 25 outbound and leaves inbound open (sensible).
The incompetent, smaller ISP blocks 25 inbound, but leaves outbound wide open, as well as 587 inbound open. This effectively blocks people from receiving mail directly, but it does nothing to prevent outbound spam from being sent.