Earlier quoted context omitted.
You can use services like mailgun to send an email, so it's not a strict requirement
You can but that multiplies complexity somewhat. I have spent 25 years dealing with outbound email from various things from country level ISPs down to small web apps and the only way to not die inside a little is to send via one of the larger providers (O365/Google/iCloud/Yahoo/AWS SES etc). I had to even dump Fastmail because they had delivery issues with Yahoo.
Overall, it seems to be a minimal cost.
On top of that, this is talking about self-hosting, for which the delivery is not a concern at all, the target of the emails is "yourself" (can add filters to avoid things reported to spam)