Email Authentication Protocols

Rajat K

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May 28, 2025
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What is a SPF Record and How to Set It Up?

SPF (Sender Policy Framework)
is an email authentication protocol that tells receiving email servers whether an email is sent from a trusted source authorized by the sender.

It is implemented by adding a TXT record to a domain's DNS records. The TXT record specifies which servers or IP addresses are allowed to send emails on behalf of your domain.

Think of SPF like a bouncer at a club - only the approved guests get in.

A Typical Example of an SPF Record

v=spf1 +mx +a include:spf.protection.outlook.com -all

v=spf1 +mx include:sendgrid.net ~all

Breaking Down the Elements for Clear Understanding
  • v=spf1 indicates this is an SPF version 1 record (the current standard).
  • +mx allows mail from the IP addresses of the domain’s MX servers.
    (These are the mail servers your domain uses to receive mail.)
  • +a indicates allow mail from the domain’s A record IP address (usually the main IP of your website or server).
  • include:spf.protection.outlook.com
    Allows emails from all Microsoft Outlook/Office 365 authorized servers.
  • -all
    Means mail from any other servers not listed here should be rejected outright.
  • ~all
    Means a soft fail, emails from servers not listed should be treated as suspicious, but not rejected outright.
In plain English, your domain is essentially saying: "Hey, these servers are allowed to send emails as me."

Tools to check for SPF records:
Got questions or want help setting up your SPF record? Drop a comment below, let’s make sure your emails always land where they should: the INBOX.