How to Set Up DKIM for Postmark

Publish a DKIM TXT record provided by Postmark to enable cryptographic signing of your transactional email.

Quick Answer — The Record You Need

Record Type

TXT

Host / Name

20xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx._domainkey

Value

v=DKIM1; k=rsa; p=YOUR_PUBLIC_KEY_FROM_POSTMARK

Postmark generates a unique DKIM selector and key for each domain. Copy the exact values from your Postmark dashboard.

Step-by-Step Setup

Log in to Postmark

Go to account.postmarkapp.com and sign in.

Select your domain

Go to your domain under Sender Signatures or Domains. Postmark displays the DKIM record details.

Copy the DKIM record

Postmark provides a TXT record with a unique selector (a long alphanumeric string) and the public key value.

Add the TXT record to DNS

Create the TXT record in your DNS provider using the selector and value from Postmark.

20xxxxxxxx._domainkey.yourdomain.com  TXT  "v=DKIM1; k=rsa; p=MIGfMA0GC..."

Verify in Postmark

Click "Verify" in Postmark. Once DNS propagates, Postmark will confirm DKIM is active.

Common Gotchas

Postmark uses a long, unique alphanumeric selector for DKIM. Do not try to guess it -- copy it exactly from your Postmark dashboard.
Postmark DKIM uses a TXT record. Some DNS providers have character limits for TXT records. If you encounter issues, check if your provider supports long TXT values.
Postmark supports DKIM key rotation. When rotating, add the new DKIM record before removing the old one to avoid a gap in signing.

Verify Your Setup

After adding your DNS records, use our free DKIM checker to verify everything is configured correctly. DNS changes typically propagate within minutes, but can take up to 48 hours.

Frequently Asked Questions

What DKIM selector does Postmark use?

Postmark generates a unique alphanumeric selector for each domain. It is a long string like 20xxxxxxxxxx. Check your Postmark dashboard for the exact selector.

Is the Postmark DKIM record a TXT or CNAME?

Postmark uses a TXT record for DKIM, containing the public key directly in the DNS record value.

Can I rotate DKIM keys in Postmark?

Yes. Postmark supports DKIM key rotation. Generate a new key, publish the new TXT record, verify it, then remove the old record.