What is SPF and Why is it Important

SPF or Sender policy Framework

SPF or Sender Policy Framework is a technical layer to filter out spammers from spamming, spoofing, and phishing email users. It helps in authenticating emails to scale the delivery rates and multiply open and click rates. Let's look into how Sender Policy Framework (SPF) can help achieve that, and its benefits and limitations.

Table of Content

What is SPF?

SPF or Sender Policy Framework is a form of email authentication that determines the mail servers allowed to deliver mails for your domain. SPF helps defend your domain from spoofing and will ensure the proper transmission of your messages. Mail servers that have received an email from your domain use SPF to check the messages that appear to come from your domain are really from your domain.

Benefits of SPF

When email was still a relatively new and exotic concept, a few people found ways to benefit from it using forgery. Recipients would get mails from reputed bank domains asking for sensitive data with a sense of urgency and then exploit them.

  • SPF helps you avoid being the victim of getting blocked for forgery you never performed.
  • When sending emails on a grand scale, the reputation of your organization’s name is paramount to the success of your email campaigns. It is important that you have SPF implemented in order to avoid high bounce rates and guaranteed delivery into your subscriber’s inbox.

SPF is beneficial for email marketing, but how does every nut and bolt function in this framework?

How does SPF work?

The method by which an SPF functions is via Simple Mail Transfer Protocol (SMTP). The process can be broken down as follows:

1. Publishing SPF record

The domain's administrator publishes a record containing all the mail servers allowed to send emails from that particular domain name. This record is called the SPF record. The record contains IP addresses that are verified to send emails on behalf of their domains.

2. Comparing IP addresses

When the receiving server senses an incoming email, the email provider evaluates the mail sender's IP address with the authorized IP addresses defined in the SPF record.

3. Deciding the authenticity of the email

Your recipient's server will evaluate your IP address, and the two servers exchange relevant information before your server sends your SMTP mail.

4. SPF email check result

If the addresses are not the same, the SPF check fails, and the email provider decides to accept, reject or mark the message as spam.

What is an SPF record?

SPF record can be viewed as a book containing all IP addresses that can send emails using a domain name. For example, if you send your transactional email from your in-office server and use Mailmodo's email service for your promotional emails, you must approve both of these server addresses as your authorized senders. SPF record can be set up by adding a distinct TXT record that is part of a domain's DNS (Domain Name Service).

How to add an SPF record?

The SPF record specifies which mail servers are allowed to send Mail to your domain. A single domain can use only one TXT record for SPF. However, multiple servers and domains that are allowed to send Mail to a domain may be listed in the TXT domain record. Follow the given steps to add an SPF record:

1. Collect IP addresses

You might be using various servers to send emails for your domain like your web server, your ISP's mail server, or any other third-party mail server used to send emails on behalf of your brand. Collect the IP addresses of all the servers that you use to send emails from. Once you have done this, you have an overview of all the servers that you use for sending emails from your domains and for which ones you need to create SPF records.

2. How to write TXT format

You can start by entering the SPF version. After you have set up your SPF record which contains v=spf1, followed by the IP address, e.g. v=spf1 ip4:, here 'v' is the element and 'spf1' is the most common version of SPF that is understood by mail exchanges, and 'ip4:' is a random IP address.

3. Add a new domain name.

Locate the page where the TXT records for your domain are updated. Add whichever new mail server you desire to include and publish it following the above syntax.

4. Check for errors

Within 72 hours, your list will be updated with the new IP addresses. Ask someone who has got a message from your domain to open it and view the text's full header. Then search the message header for SPF results. If the header indicates that the SPF failed, check the errors in your SPF record.

SPF, DKIM, and DMARC are all ways to authenticate your mail server. These spam protection methods are becoming increasingly popular and might become a compulsory measure against junk emails someday. Not only that but confirming your account with these methods will make you a legitimate sender in the eyes of the receiving end server.

  • DKIM is an acronym for "Domain Keys Identified Mail". It also goes by the name of "email signing". DKIM facilitates an encryption key and digital signature that verifies that an email message was not forged or altered, building trust between the sender and receiver servers. It means that no one in between can tamper with any of the emails going from one server to another.
  • DMARC is an acronym for "Domain-based Message Authentication, Reporting, and Conformance". It's an email authentication, policy, and reporting protocol formed by combining both SPF and DKIM. A DMARC policy applies clear instructions for the message receiver to follow if an email does not pass SPF or DKIM authentication.

How does SPF help expand your reach?

Spammers will try to send unwanted emails, whenever they can take control of your domain. This will harm your credibility and damage deliverability. You should make it a priority if you have not authenticated your domain. This is how SPF helps take care that your deliverability is high.

  • An SPF record will ensure that spammers can't send emails using your domain name. Hence the chances of your domain getting blacklisted are diminished.
  • When email receivers establish trust in your brand due to the use of SPF, your future emails will find a secure entry in their inboxes.
  • Some email recipients strictly desire an SPF record and would otherwise mark emails as spam if they don't compulsorily have one or it might result in email bouncing.
  • Sender Score

    is a score of every outgoing mail server using conventional email metrics such as unsubscribes and spam files. SPF majorly helps to increase your Sender Score, and in turn, helps email deliverability.

SPF does look like a one-stop solution for preventing spamming, spoofing, and phishing, but you do want to take care of a few drawbacks.

Limitations of SPF

There are a few constraints of the SPF system. They are as follows:

  • Forwarded emails usually fail the sender policy framework test as they do not contain the original senders' information and appear to be a spam message.
  • Many domain administrators might not be able to update their SPF record regularly.
  • The domain using a third-party email provider must update the SPF record even when the service provider changes its servers, which is extra work.
  • SPF verification is done on the Mail From (MFrom) domain, which will not be visible to the recipient. Hence the recipient system can't wholly rely on SPF results.
  • SPF authenticates email domains buried deep in the message headers and can mislead the end-user which means that SPF will approve of domain names that might not be visible to the user.

Email providers are aware of these threats and hence try their best to minimize damage as much as possible.

SPF for AMP Email approval from Email Clients

If you want to reap the benefits of sending out interactive AMP emails, you will have to get whitelisted with Yahoo Mail, Gmail, and Mail.ru which support AMP emails. For a successful whitelisting of your sender address, these email clients require SPF before approving your email address.


SPF protects the envelope sender and stops spammers from abusing mail systems to trick innocent users. 1 in 6 emails gets sent to the spam or blocked from your subscribers' inbox altogether, leading to only 83% conversion. Mailmodo will help you live up to your full potential. Our email experts will help you get your security certifications done and improve your deliverability to yield the best results.

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