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    Chapter · DKIM for Postmark
    Revised 17 Jun 2026
    Guide · DKIM · Postmark

    How to set up DKIM for Postmark.

    Postmark is a transactional-only ESP with strict acceptable-use enforcement. Their authentication setup is the simplest of the major ESPs.

    Afsan Rahmatullah
    Afsan RahmatullahMailerMonk

    DKIM (DomainKeys Identified Mail, RFC 6376) is the cryptographic signature attached to outgoing email so receivers can verify the message wasn't tampered with and that it actually came from a server authorized by your domain. To turn it on for Postmark, you publish one or more DNS records at `<selector>._domainkey.<your-domain>` containing the public key matching the private key Postmark uses to sign.

    Most ESPs (including Postmark) ask you to publish CNAME records that point at hosted keys they manage. This is preferable to publishing the raw key text yourself — when the provider rotates keys, your DNS keeps pointing to the rotated key and nothing breaks.

    Publish these DNS records

    Add the following record(s) to your domain's DNS zone. Most registrars (Cloudflare, Route 53, Namecheap, GoDaddy) accept values exactly as shown.

    Record · TXT
    Type
    TXT
    Host
    <token>._domainkey
    Value
    k=rsa; p=<KEY_FROM_POSTMARK>
    Why this matters
    • Postmark issues a per-domain selector token (e.g. `20231201abcd`). The DKIM record is published as TXT containing the raw RSA public key.
    • Postmark also offers DKIM rotation; when you rotate, the new key is issued under a new selector and the old selector stays valid for ~30 days for in-flight signatures.

    Where in Postmark

    The DKIM configuration lives in Postmark → Sender Signatures → Add Domain → DNS.

    Verify the records

    After the records propagate, run the DKIM Checker against your domain with each selector to confirm the public key resolves and parses correctly.

    From a terminal
    dig +short TXT <selector>._domainkey.your-domain.com
    Run the free DKIM checker

    Common pitfalls

    Pitfall
    • Postmark's anti-spam team will pause your account if you send marketing mail through it. Use a separate ESP for newsletters or promotional content.
    • The Return-Path on Postmark mail is `pm.mtasv.net` by default. Set up a custom Return-Path domain for SPF alignment if you need DMARC to pass on SPF as well as DKIM.
    After you publish

    Want to know if it actually keeps working?

    MailerMonk continuously watches your DKIM record, aggregate DMARC reports, and inbox placement — and pings you the moment something drifts. Free for the first domain.

    Start free trial

    About the author

    Afsan Rahmatullah
    Afsan Rahmatullah
    MailerMonk

    Building tools that keep cold email out of spam. Writes about deliverability, DMARC, and what actually moves inbox placement.

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