Delegating mail to an external service means you're not self hosting it.
Sending email is something you can just do. There's no need for an external service unless:
- You're trying to deliver email to external users.
- You really need your email to get through without ending up in people's spam folder.
No.
Having a couple emails end up in spam boxes isn't that big a deal for many self-hosted app scenarios.
For example, if you have a limited set of users, the setup process can involve getting an email and marking it not spam.