Both send email over a REST API. Every row below was read from Rasket's own pages and Postmark's own pages, and the day they were read is printed under the table.
Rasket is an email API for developers: one REST API and a dashboard for transactional email and campaigns, with inbound mail, signed webhooks and an MCP server in the same product and on the same key.
Postmark is a transactional email service with six official libraries, an SMTP option and Message Streams, which keep transactional and broadcast mail on separate sending infrastructure.
| Criterion | Rasket | Postmark |
|---|---|---|
| Sending and receiving | ||
| Inbound email | Pro and Platform | |
| Transactional and campaigns on one plan | Yes · on a separate Broadcast stream | |
| Idempotent sends | Not published | |
| Versioned templates | Not published | |
| Automations | Not published | |
| SMTP relay | ||
| DKIM key size | 2048-bit | Not published |
| Webhooks and developer tools | ||
| Signed webhooks | – | |
| Replay a webhook event | Not published | |
| MCP server | Not published | |
| Markdown docs and llms.txt | llms.txt only | |
| Official SDKs | Coming soon | 6 languages · incl. Node.js, Python, Java |
| Plans and pricing | ||
| Free plan | 3,000 / mo · 100 a day | 100 / mo · does not expire |
| Entry paid plan | $20 / mo · 50,000 emails | $15 / mo · 10,000 emails |
| Extra emails, per 1,000 | $0.60 · down to $0.25 on Scale | $1.80 · on Basic |
| Data retention | 30 days | 45 days · up to 365 with an add-on |
| Dedicated IP | $30 / mo · on Scale | $50 / mo · Pro and above |
| Best for | Developers who want sending, receiving and campaigns behind one API key | Teams who want transactional and bulk mail kept on separate streams |
Facts checked on against each company’s public pricing and documentation.
Postmark keeps 45 days of history where we keep 30, and sells that up to a year as an add-on, so if you are chasing what happened to a receipt three months ago their default reaches further back than ours. They publish six official libraries, including .NET and Java, while ours are still coming. Message Streams are a deliberate design rather than a limitation: keeping bulk mail on separate infrastructure from receipts is a defensible way to protect a transactional reputation, and some teams want exactly that separation.
Postmark is best for: Teams who want transactional and bulk mail kept on separate streams
One row here is not a matter of taste. Postmark's own webhook guide says they do not sign webhooks and asks you to use basic authentication and an IP allowlist instead; Rasket signs every event with a timestamp and a secret, and lets you replay one from the dashboard. After that it is price and reach: $15 buys 10,000 emails on Basic and $55 buys 50,000, against $20 for 50,000 on Rasket, with extra mail at $1.80 a thousand against $0.60, and inbound arriving on their Pro tier but on every plan of ours. Postmark is the better fit if you want longer retention by default or a client library in a language we have not shipped.
Rasket is best for: Developers who want sending, receiving and campaigns behind one API key
Yes, and the webhook row is the reason most teams look. Postmark's documentation states that they do not sign webhooks with HMAC; Rasket signs every event and you can replay one from the dashboard. Rasket also includes inbound mail on every plan and charges $0.60 per extra thousand against $1.80. Postmark keeps history longer by default — 45 days against 30 — and has more client languages, so weigh those before moving.
Postmark: On the Pro and Platform plans. The pricing table lists inbound email processing against Pro and Platform. Rasket receives mail at your own domain on every plan, including the free one, and delivers each message to a signed webhook with its headers, text, HTML and attachments.
At 50,000 emails a month Postmark's Basic plan is $55 and Rasket's Pro plan is $20. Both figures are read from the two price lists on the same day and both cover the same volume, so this is the comparison's widest price gap; past the quota it stays open, at $1.80 a thousand against $0.60. What the extra buys on Postmark is 45 days of retention rather than 30, and Message Streams keeping bulk mail on separate infrastructure.
Yes. Point any app that sends over SMTP at smtp.rasket.com on port 465 or 587, with the username rasket and an API key as the password, and each message becomes an ordinary API send: the same verified domains, suppressions, quota and webhooks. Moving an SMTP integration is a change of host and credentials, not of code.
Add the domain in Rasket and publish the generated DKIM, SPF and DMARC records; verification runs on its own and you can keep sending through Postmark meanwhile. Then swap the call — POST /emails carries the same fields as their email endpoint, and a template alias becomes a Rasket template published as a version. Over SMTP, the server token you log in with becomes the username rasket and a Rasket key, and the host becomes smtp.rasket.com. Point your webhook handler at Rasket's signed events, verify the signature rather than the basic-auth credentials you were checking, and replay a delivery from the dashboard to test it.
Rasket, on what each publishes. Postmark serves an llms.txt index of its documentation, which is genuinely useful to an assistant reading up on the API, but on the day we checked there was no MCP server and no Markdown twin at a documentation URL. Rasket publishes an MCP server with seven toolsets, a setup skill, Markdown at every docs URL, llms.txt and llms-full.txt, so an agent can configure a domain and send without a person pasting a key.
Create a key, verify a domain, and send your first email the same morning. The free plan does not expire.