head to head
Postmark vs Mailgun
Transactional deliverability specialist versus flexible developer email infrastructure.
What matters for teams building autonomous agents
An agent stack treats email as a two-way primitive. Inbound has to arrive as structured JSON a tool call can consume, sends have to be safe to retry when a model loop repeats itself, and every action needs an audit trail. A provider without inbound parsing only solves half the problem.
| Priority | Postmark | Mailgun |
|---|---|---|
| Inbound parsing | Yes | Yes |
| Idempotency keys | No | No |
| Webhooks | Yes | Yes |
| Operating since | 2010 | 2010 |
| Event stream | Yes | Yes |
| Best published rate per 1,000 | $1.50 | $0.70 |
| Batch sending | Yes | Yes |
| SDKs | node, python, go, ruby, php, java, elixir, rust, dotnet | node, python, go, ruby, php, java |
| Multi-tenant | Yes | Yes |
For an agent that reads and writes email running inbound parsing into tool calls and model-generated sends that must not duplicate, the split is even: Postmark takes SDK breadth, Mailgun takes best published rate per 1,000. Neither pulls ahead on this audience's priorities. That ordering reflects this audience. Weigh the same table differently and the answer changes.
Side by side
| Feature | Postmark | Mailgun |
|---|---|---|
| Webhooks | Yes | Yes |
| SDKs | node, python, go, ruby, php, java, elixir, rust, dotnet | node, python, go, ruby, php, java |
| Multi-tenant | Yes | Yes |
| Tagline | Transactional-only, fast and well-delivered. | Developer-leaning email infra, owned by Sinch. |
| Free tier | 100/mo developer plan | 100/day permanent free plan |
| Starts at | $15/mo for 10,000 emails | $15/mo for 10,000 emails (Basic) |
| Pricing model | tiered | tiered |
| API | Yes | Yes |
| SMTP | Yes | Yes |
| Templates | rich | rich |
| React Email | No | No |
| Inbound | Yes | Yes |
| Idempotency | No | No |
| Dedicated IP | Yes | Yes |
| Deliverability | Strong transactional reputation with separate streams for transactional and broadcast traffic, which helps protect sender reputation. | Generally good, with deliverability monitoring tools available on higher tiers. Inbound routes and suppressions are battle-tested. |
| DX score | 9/10 | 7/10 |
| Best for | Teams where password resets, receipts, and magic links absolutely cannot miss the inbox. | Technical teams that want SMTP relay plus advanced routing. |
Postmark
pros
- ›Transactional-only routing and strong operational history
- ›Streams cleanly separate transactional and broadcast
- ›Free DMARC monitoring product (dmarc.postmarkapp.com)
- ›Retains full message content and metadata for 45 days for debugging
cons
- ›No idempotency keys
- ›Pricing per email is higher than SES, Mailgun, or SMTP2GO
- ›No drag-and-drop template builder
- ›Marketing automation is intentionally absent
Mailgun
pros
- ›Strong SMTP relay support, useful when migrating off self-hosted Postfix
- ›Inbound routes with regex matching
- ›Validation and parsing tools available
- ›Sub-accounts for agency use cases
cons
- ›Overage pricing and plan differences need close review at scale
- ›Documentation is comprehensive but occasionally out of date
- ›No idempotency keys
- ›Sinch ownership has moved focus toward enterprise