What is SPF?

What is SPF?

Sender Policy Framework (SPF) is a way for email service providers to verify that a mail server is authorized to send email for a domain. By publishing the SPF record in DNS that includes spf.mtasv.net (which lists all of Postmark's mail servers), you let recipients of your emails know that Postmark is authorized to send email for your domain.

Why should I have an SPF record?

You get better email deliverability when sending messages through Postmark. While SPF isn't required, having emails that pass SPF authentication appear more legitimate to your recipients and are less likely to go to Junk or Spam folders. Additionally, passing SPF is required for "Domain-based Message Authentication, Reporting & Conformance" (DMARC), a newer standard to reduce email spoofing which builds on top of SPF and DKIM.

How does SPF work?

SPF records are DNS records of type TXT with a special format. If you're setting up SPF for a brand new domain, we suggest you use the following SPF record:

  v=spf1 a mx include:spf.mtasv.net ~all

This record will authorize several different IP addresses to send email for your domain:

  • the result of the A DNS record for your domain.
  • the result of the MX DNS record for your domain.
  • the IP addresses listed by spf.mtasv.net (which are the IP addresses that Postmark sends email from).

If you have an existing SPF record for your domain, you can modify it to authorize Postmark as well. For example, if your domain uses Google Apps for email, you might have an SPF record that looks like:

  v=spf1 a mx include:spf.google.com ~all

To also authorize Postmark to send emails for your domain, you would modify the record to look like:

  v=spf1 a mx include:spf.google.com include:spf.mtasv.net ~all

You can find more in-depth information about SPF in our SPF guide.

When it comes to email authentication, SPF is just one aspect. Read our articles on DKIM and DMARC to get the full picture.

Last updated April 29th, 2016

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