How to set up SPF, DKIM & DMARC for Postmark

Postmark needs exactly two records: a DKIM TXT unique to your account, and a return-path CNAME whose target is the same for everyone — pm.mtasv.net. The custom return-path is what makes SPF align.

DKIM

The selector is generated per domain (it looks like a timestamp followed by pm).

Type	`TXT`
Host / Name	`20260713120000pm._domainkey` Your exact selector host is shown on Postmark's DNS settings page.
Value / Content	`k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8A…` Example only — copy both host and value from Postmark → Sender Signatures → your domain → DNS Settings.

Return-Path (covers SPF)

The target below is fixed — only the host is your choice (pm-bounces is Postmark's default suggestion).

Type	`CNAME`
Host / Name	`pm-bounces`
Value / Content	`pm.mtasv.net`

Postmark → Sender Signatures → add your domain.
Publish the DKIM TXT it generates and the pm-bounces CNAME above.
Click Verify on both rows; set the custom Return-Path as default for the domain.

DMARC

DMARC is per-domain, not per-provider — one record at _dmarc.yourdomain.com covers Postmark and everything else that sends as you. Start in monitor-only mode:

Type	`TXT`
Host / Name	`_dmarc` Some providers want the full _dmarc.yourdomain.com here.
Value / Content	`v=DMARC1; p=none; rua=mailto:your-report-address` Example only — replace your-report-address — our DMARC generator builds the record, or sign up free and we generate it with a report address that feeds your monitoring dashboard.

Provider note: DKIM aligns via the generated key; the custom return-path CNAME makes SPF align too. No SPF TXT record is needed for Postmark.

Full walkthrough: how to set up DMARC without breaking your email, and why aligned authentication is what DMARC actually checks.

Verify it worked

After DNS propagates (minutes to an hour), send a message from Postmark to our inbox test — it shows the real SPF/DKIM/DMARC verdicts a receiver computes, including whether authentication aligned with your domain. Then HealthCheck Email keeps checking daily and alerts you when a record breaks.

Records current as of 2026-07-13. Provider dashboards change — the authoritative reference is Postmark's official docs.