I do. Though I am self hosting it to have my personal email, being well... personal. Not for my company so maybe I am not the target.
Interesting project though. I always felt missing API to just send emails from some script in my mail server.
Posthorn is built for the opposite end of that, you've already decided you want to use a transactional provider for app mail and you just want to stop having to deal with wiring it into all of the things. Obviously for a big production app you build your own mail service, but for gluing together a bunch of different apps you're self hosting, I think this makes sense and addresses a real issue.
If you want an API piece to augment what you already have, Posthorn might still be useful regardless of how the rest of your mail is set up. A Posthorn JSON endpoint is just a POST with Bearer auth and an idempotency key. Example from my docs:
curl -X POST https://posthorn.yourdomain.com/api/transactional \ -H "Authorization: Bearer $WORKER_KEY_PRIMARY" \ -H "Content-Type: application/json" \ -H "Idempotency-Key: reset:user-123:$(date -u +%FT%H)" \ --data '{ "to_override": "bob@example.com", "subject_line": "Reset your password", "message": "Click here: https://app.example.com/reset/abc" }'
Could run alongside your existing mail server. It's a small enough overhead that the juice might be worth the squeeze.
This is the exact case where I'd be really afraid of running it on my own and this I VERY STRONGLY BELIEVE should NOT be the case. Participating in email should be easy.
Anyway yeah it looks interesting. In theory I could start it up with my mail server, which already is using docker compose, configure it and use API for sending emails.
I will give it a try.
Let me know how it works out for you, happy to help in any way I can. Also feel free to make any feature requests or open an issue on GitHub.
I do not remember if I have ever used the GNU mail program that is available on Linux, but my e-mail server is hosted on FreeBSD, so I have used very frequently the FreeBSD CLI utility to send e-mail messages from scripts.
Moreover, all FreeBSD servers come configured by default to send automatically a variety of e-mail reports to the administrator, to inform about incidents or statistics, so there are a lot of examples of usage from scripts.