What is SPF?

Sender Policy Framework (SPF) is a type of DNS record that Mail Administrators use to delegate email delivery options to 3rd parties.  SPF allows the owner of a domain to set a range of IP addresses and domains that are authorized to send email on behalf of that domain.

spf-simple

A simple SPF record (Google.com)

For example, you might use a 3rd party bulk emailer like Mailchimps or MailGun to send a weekly newsletter.  You would want your SPF record to include IP addresses that would be sending for you.

spf-complex

A more complex SPF record with multiple sending IPs and 3rd party delivery services included (anonymous).

How does SPF work?

Essentially, you setup an SPF record to reflect any IP addresses that will be sending on behalf of your domain.  If you have an SPF DNS record, it is publicly discoverable. When an email is sent purporting to be from your domain the recipient server checks your SPF record to see if the sender is actually authorized to send on your behalf.  If so, the email recipient knows the email is from you or your delegates and will chose to accept based upon your email reputation.  If not, the email recipient can opt to scrutinize the email more carefully, quarantine it or outright reject the email.  In this way, SPF is a powerful tool in the ongoing battle against SPAM.

Who should have an SPF record?

Everyone should be using SPF, but particularly companies that utilize any 3rd party email services to send email.  Since many companies actively check SPF records now when processing email, a failure to have an SPF record may mean that your email, especially bulk email, maybe denied.

SPF is a key component to email security and reducing spam and as such, everyone should setup an SPF record to ensure the best possible delivery of their outbound email.  MxToolbox provides a free SPF checking tool (pictured below) where you can verify that your SPF record is publicly accessible that also checks your record against the RFCs for syntax and best practices.

spf-lookup

Results for Google’s SPF record lookup including our checks of record syntax and setup.

SPF is required for implementing Dmarc.  If you are interested in getting started with Dmarc, we suggest implementing SPF immediately or double-checking your SPF setup and then setting up a Dmarc record that points to our new Dmarc reporting tool.

As a paid MxToolbox.com user, you get access to our expert Support team.  Open a ticket to get access to the best advice on improving your email delivery including setting up SPF and implementing DKIM and Dmarc.

2 thoughts on “What is SPF?

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