How to Set Up DMARC for Fastmail

Publish a DMARC record to protect your custom domain when using Fastmail for email.

Quick Answer — The Record You Need

Record Type

TXT

Host / Name

_dmarc

Value

v=DMARC1; p=none; rua=mailto:[email protected]; ruf=mailto:[email protected]; fo=1

Fastmail provides SPF and DKIM alignment by default when properly configured.

Step-by-Step Setup

Configure SPF and DKIM

Set up SPF (include:spf.messagingengine.com) and DKIM (fm1/fm2/fm3 CNAMEs) for Fastmail.

Test email authentication

Send a test email from Fastmail and verify SPF and DKIM pass in the headers.

Create the DMARC record

Add a TXT record at _dmarc.yourdomain.com.

v=DMARC1; p=none; rua=mailto:[email protected]; ruf=mailto:[email protected]; fo=1

Monitor reports

Review DMARC aggregate reports. Fastmail typically has clean alignment.

Enforce the policy

Fastmail provides good alignment. After confirming, move to p=quarantine and then p=reject.

Common Gotchas

Fastmail provides both SPF and DKIM alignment, making it well-suited for strict DMARC policies.
If you use Fastmail as your only email sender, you can move to p=reject relatively quickly after monitoring.
If you use Fastmail with other services (mailing lists, marketing tools), ensure all are authenticated first.

Verify Your Setup

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

Frequently Asked Questions

Does Fastmail support DMARC alignment?

Yes. Fastmail provides both SPF and DKIM alignment when properly configured with a custom domain.

Can I use p=reject with Fastmail?

Yes. Fastmail has excellent authentication support. If Fastmail is your only sender, you can safely use p=reject.

Does Fastmail manage DMARC automatically?

If you use Fastmail's nameservers, they can set up the DMARC record for you. Otherwise, add it manually to your DNS.