OpenHelm Mail · Developers
Transactional email your app can actually use
REST for the code you control, and SMTP for everything that will only ever speak SMTP. One credential, and a sending budget that a marketing campaign can never spend.
The situation.
Plenty of what needs to send email cannot call your API. Supabase Auth, your database, your CI, and half the tools you already run speak SMTP and nothing else, which is why most teams end up with a second mail provider.
How it works.
SMTP, because some things only speak SMTP
Supabase Auth, Postgres and CI cannot be talked into a REST call. The gateway takes a real SMTP submission, always authenticated, never an open relay.
One credential for both
The SMTP password is an OpenHelm API key, so a single revoke stops REST and SMTP together. There is no second secret to forget about.
Your From is honoured or refused
A From header naming an address you do not own is rejected, not quietly rewritten to something else. You always know what your users will see.
Separate daily budgets
Transactional, agent and marketing mail are counted separately per address. An outreach campaign running away cannot make a password reset fail.
Reply-To is evidence, not assumption
A reply address is only used when the domain is confirmed to receive; otherwise it falls back to an address that does, and says which and why. A verified sending domain does not imply a working MX.
No unsubscribe where it would be wrong
Transactional mail carries no unsubscribe header. Letting somebody opt out of their own password reset is a support incident, not a feature.
What you actually do. Once.
Verify your domain
DKIM so you send as yourself, with your own reputation isolated from every other sender.
Point your app at it
REST from your own code, or SMTP host, port and your API key as the password for anything that cannot.
Send
Every send returns what actually happened: delivered, held, or refused with the reason. Bounces and complaints come back as events and suppress the address.
Questions
Can I use this for Supabase Auth emails?
Yes, that is one of the reasons the SMTP gateway exists. GoTrue speaks SMTP only, so a REST-only provider cannot serve it.
Is SMTP an open relay?
No. Authentication is mandatory, the credential is an API key, and the From header must name an address your organisation owns.
What happens if a recipient has bounced before?
They are suppressed, and a send to them is refused by name rather than silently dropped. If some recipients of a message are suppressed and others are not, the deliverable ones go and you are told which were dropped.
Can I send bulk mail through this?
Bulk mail is a different send class with its own budget and a required one-click unsubscribe. Sending it as transactional to avoid that is not something the platform will do for you.
Give your agents a real email address.
Inboxes on your own domain, replies that wake the agent handling them, and a person in the loop wherever you want one.