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Postmark specialises in transactional email and is known for fast, reliable delivery. It keeps transactional and bulk mail strictly apart, which is a good fit for a store whose email is entirely order confirmations, shipping notices and password resets. Spree talks to Postmark over plain SMTP, so there is nothing to install — see Emails for how the configuration works.

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Configuration

The Server API Token goes in both the username and the password field — the same value twice. This looks like a mistake but is exactly what Postmark documents.
Postmark accepts ports 25, 587 and 2525, all using STARTTLS. Use 587 unless your host blocks it, in which case 2525 is the usual fallback. Postmark has no implicit-TLS port — setting SMTP_PORT=465 out of habit produces a connection that hangs rather than a clear error.

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Getting a Server API Token

  1. In the Postmark dashboard, open the server you want to send from.
  2. Go to the API Tokens tab and copy the Server API Token.
Tokens are per server, so mail from each server is tracked and rate-limited separately. A separate server for staging keeps test mail out of your production activity log.

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Message streams

Postmark separates transactional streams from broadcast streams, and keeps their reputations apart. Mail sent through smtp.postmarkapp.com with a Server API Token goes to the default transactional stream unless a header says otherwise, which is what a Spree store wants — there is nothing to configure. Broadcast mail uses a different host, smtp-broadcasts.postmarkapp.com, which Spree does not need.

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Authenticating your domain

Go to Sender Signatures → Add Domain, then add the DKIM and Return-Path records Postmark generates at your DNS host. Once verified, set SMTP_FROM_ADDRESS to an address on that domain.
New Postmark accounts are reviewed before they can send to customers. Until the account is approved you can only send to domains you have added and verified, which behaves much like a sandbox: real customer addresses are refused. Approval usually takes under a day on weekdays, and only the account owner can request it. Ask as soon as you create the account rather than on launch day, and be ready to describe what your store sends — Postmark enforces its transactional-only policy more strictly than most providers.