My 2 cents:
I’ve been a sysadmin for 30 years, switched to DevOps about 13 years ago, I have maintained my own server al these years so the setup of discourse 3 months ago was no biggy for me, expecially that now it’s done in docker, and yet it did take about 3 days to finalize the email interface issues.
running your own server these days, even with DKIM, SPF and all the other TLAs, it’s still impossible to stay afloat and not fall into an RBL just because some big faceless corp decided to block a Class B your VPS is sitting in at a data center across the world. There’s no escaping paying for a relay service. I looked as a few, I use mailjet for my own mail but the free tier was not enough and the price cliff is pretty painful for my pocket. I discovered AWS SES was the cheapest solution and it worked great ever since. I wish I could use it for all my emails, but it’s not really made for that.