Transactional Email · Integration
Postmark
Add Postmark to your product for your customers, and give your AI agents governed access to it.
Postmark is deliberately narrow: it sends transactional email and keeps it separate from bulk, and it enforces that separation with different message streams. That constraint is the reason it is worth integrating rather than a limitation to work around, because a receipt and a newsletter should not share a reputation. Servers are the isolation unit and each carries its own token, which maps cleanly onto per-customer connections. Templates are held server-side and rendered on send, so your product passes a model rather than assembled HTML. Bounces are first-class objects rather than log lines, which makes the failure path something you can build on. fastn holds each customer's server token and keeps the connector current.
In your product
Embedded for your customers. Per-tenant auth, no per-customer code, maintained by fastn.
Let a customer connect their own Postmark server so transactional mail sends under their token and their reputation.
Send with a server-side template so your product passes a model rather than building HTML.
Read bounces and spam complaints as records, so a failed send becomes something your product can act on.
Keep transactional and broadcast streams separate, which is the reason a receipt still lands in the inbox.
For your AI agents
Governed, audited access for the agents you build, through the MCP server.
An agent looks up why a specific message bounced and reports the reason in plain language.
An agent reactivates a bounced address within governed permissions, with the action audited per tenant.
An agent reads open and click activity for a template and reports which one is failing.
Example prompt
Why did the password reset email to this address fail, and has it bounced before?
Set up Postmark in 4 steps
- 01Enable the Postmark connector from your fastn dashboard.
- 02Have each customer authorise their own Postmark account, so calls run under their credentials rather than a shared key.
- 03Decide which messages, templates and delivery events your product needs, map those fields, then enable the actions and triggers you want.
- 04Call it from your product and expose it to your agents through the same governed connection.
Why teams use the Postmark integration
What you get by embedding it with fastn instead of building it yourself.
- Ship a Postmark integration without building it. Your customers connect their own Postmark account inside your product and work their messages, templates and delivery events there, with no per-customer code on your side.
- Handle the part that actually costs time: deliverability is the whole game, and it is decided by bounces, complaints and the reputation of the sending domain rather than by anything in the send call. fastn owns the auth, token refresh, rate limits, pagination and breaking-change fixes, so a Postmark update is not your on-call problem.
- One integration serves your product and your agents. The same governed Postmark connection powers in-product features and gives AI agents scoped, audited access, so you send the mail your product owes its users and know what happened to it without wiring it twice.
Used by these teams
Compare with
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StripePostmark integration FAQ
How do I add a Postmark integration to my product?
Enable the Postmark connector in your fastn dashboard, then let each customer authenticate their own Postmark account. fastn handles the OAuth flow, token storage and refresh per tenant, so there is no Postmark client code in your app and no per-customer branch in your codebase. Setup is 4 steps.
Do my customers each connect their own Postmark account?
Yes. Every connection is scoped to the individual customer, so each authorises their own Postmark account and only ever sees their own messages, templates and delivery events. That per-tenant isolation is the point of an embedded integration: you support the long tail of customer setups without maintaining an integration per customer.
Can AI agents use this Postmark integration?
Yes. The same connection is exposed to your agents through the fastn MCP gateway, with permissions scoped per tenant and every call audited. An agent looks up why a specific message bounced and reports the reason in plain language.
Who maintains the Postmark integration?
fastn does. When Postmark changes an endpoint, deprecates a field or alters its auth, the fix lands in the connector rather than in your backlog, and your customers' connections keep working.
Can each customer send from their own domain with Postmark?
Yes, and it is the reason to do this per tenant rather than through one shared key. Sending reputation attaches to the domain, so a customer sending from their own verified domain in Postmark carries their own deliverability rather than inheriting yours or damaging it.
How do bounces and complaints come back from Postmark?
As records rather than log lines. Hard bounces, spam complaints and unsubscribes become suppression state you can read per tenant, so your product can stop mailing an address that already failed instead of sending into a hole and quietly burning the customer's sending reputation.
What can I build with the Postmark integration?
A common starting point: let a customer connect their own Postmark server so transactional mail sends under their token and their reputation. Teams also use it for the other use cases listed above, and expose it to agents for governed reads and writes.
How much does the Postmark integration cost?
It is included. Pricing is based on connected accounts, not on how many connectors you enable, so adding Postmark does not change your per-connector cost. You can start free with 3 connected accounts.
Add Postmark to your product
Start free with 3 connected accounts. No sales call required, and no per-customer integration code.