The Importance of SPF and DKIM in Your Email Security Strategy

Your email domain is not only a mechanism of communication; it is your digital identity. Each email you send carries with it your brand, trust, and reputation. Unfortunately, the reality is that, without appropriate email authentication, anyone can impersonate you.

This is why understanding your SPF and DKIM importance is necessary. It is a critical component of a robust email infrastructure, with each working in tandem to prevent email spoofing as well as phishing attacks. Along with DMARC, they provide businesses with the opportunity to enforce policies and stop malicious emails before they inflict damage.

However, the critical takeaway is that you should not only rely on a single layer of defence. Firewalls, spam filters, and antivirus tools will not catch everything. Businesses need to adopt a multi-layered defence to deter email spoofing, and SPF and DKIM are foundational pieces of that plan.

In other words, email security is not stopping at spam filters and antivirus software; it is building a multi-layered defence where SPF and DKIM are at the centre.

What is SPF?

SPF, or Sender Policy Framework, is one of the original and best methods of email authentication. It allows domain owners to designate which mail servers may send messages on behalf of their domain.

It is like the bouncer of your email; if a server sends a message on behalf of your domain and it is not on the list, it does not send the message.

How SPF works

For the sake of explanation, the following is a simplified illustration of SPF in action:

1. You publish a record to the DNS settings of your domain that includes a list of mail servers and their corresponding IP addresses.
2. When somebody receives an email message from your domain, their mail server will perform a check of the sender’s IP address against your SPF record. Check your SPF record now.
3. If the match is successful, the email will pass SPF; however, if there is no match, the email will fail the SPF validation.

Example SPF Record:

v=spf1 include:_spf.google.com include:spf.protection.outlook.com -all

This indicates that only the Google Workspace and Microsoft 365 servers are permitted to send mail for the domain, and the directive “-all” rejects all others.

Why SPF Matters

SPF plays a simple, but critical, role in a secure email infrastructure: it stops attackers from potentially using unauthorised servers to send spoofed emails with your domain.

Without SPF, an attacker could send you thousands of emails that look like they came from your company. With SPF, you create the rules and require servers to verify legitimacy first.

What is DKIM?

While SPF validates where the email came from, DKIM validates that the integrity of the message itself has not changed. DKIM provides proof that the content of the email has not changed in transit and that it genuinely was sent from your domain.

That makes DKIM not only a best practice for email authentication but also a key part of protecting your brand reputation.

How DKIM Works

The process may seem technical, but the idea is simple:

When you send the email, your server creates a digital signature (based on its private key) and appends it to the email header. The recipient’s server will look for your published public DKIM key, which is stored in your DNS records.

Then, the recipient’s server will use the DKIM key to verify the signature against the email content. If the signature matches, that proves the email has not been altered.

Why DKIM Is Necessary

DKIM assures that what you send to the recipient gets the same; no changes are made to links, there are no hidden changes, and no malware is added. It ensures that the content integrity of what you are sending is maintained, which is vital to prevent email spoofing and phishing attacks.

DJMK and SPF combined are required to provide an SPF DKIM setup to establish trust throughout the email ecosystem.

How SPF and DKIM Work Together

SPF and DKIM are both effective by themselves. Their true effectiveness comes in when you put them both into context under DMARC.

DMARC depends on both SPF and DKIM for emails to be authenticated. It helps tell receiving servers what to do when an email fails to be authenticated, whether to reject it, quarantine it, etc.

In order for a DMARC to pass, either SPF or DKIM must align with the domain in the “From” field. This alignment is important because it protects against attackers who can use one control against the other, and vice versa.

Why Alignment Is Important

Let’s consider that you have an SPF perfectly set up, and your DKIM is not set up, or the opposite. This gap can allow the attacker in. Actual protection is provided by configuring, aligning, and enforcing via DMARC.

This layered approach allows for a secure email infrastructure and mitigates the chances of spoofing or phishing succeeding.

Best Practices for SPF and DKIM Implementations 

SPF and DKIM setup does not have to be difficult; it just requires diligence. Here are the best practices for your SPF DKIM implementation:

1. Implementing the SPF Records

Identify all platforms that send emails on your behalf, such as Google Workspace, Microsoft 365, CRMs, marketing tools, etc. You can publish one SPF record per domain in DNS.

Keep this simple; avoid excessive “include” statements, creating complexity during validation to check all the included statements. Use “-all” at the end to ensure only the servers you authorised for email delivery will be accepted. 

2. Enabling DKIM Signing

For platforms like Google Workspace or Microsoft 365, create DKIM keys. Publish the public key in DNS as a TXT record. Ensure DKIM signing is enabled for all outgoing emails. Rotate DKIM keys periodically to maintain security.

3. Monitor and Update

You will update SPF whenever you add or remove an email service provider. Review DKIM implementations to ensure you are addressing all email streams. Use DMARC reporting to monitor activity and detect if unauthorised attempts have been made to send emails from your domain.

Common Mistakes to Avoid with SPF and DKIM

Even the most robust security policy cannot protect itself against being misused. Here are situations you will want to avoid:

1. Incorrect SPF Record Syntax

A bad record can result in SPF validation failing. A few of the common mistakes are as follows:

• Multiple SPF records for the same domain (there should only be one).
• The 10-DNS-lookup limit was exceeded. 
• Forgetting about the -all or ~all at the end.

2. Misconfigured DKIM

DKIM can fail for a few reasons. Below are a few of the most common:

• The public key is published incorrectly in DNS.
• The private key is left insecure.
• Signing messages is not enabled.

Misconfigured DKIM is as bad as not having one. It cannot protect your domain if it is misconfigured.

3. Not Using SPF and DKIM Together

Some businesses will enable either SPF or DKIM and stop. One is not enough. Attackers can exploit whichever one you do not have in place. The only way you can prevent email spoofing is to use both (aligned) with DMARC.

Conclusion

Email is still the number one attack vector for cybercriminals. As the tactics keep evolving, at their core, the tactics are similar. The core weakness is trust. Trust allows attackers to exploit the system using spoofed emails, phishing links, and forged identities.

That’s why the SPF and DKIM importance is greater than ever.

• SPF establishes which servers are authorised to send on your domain.
• DKIM guarantees the origination and integrity of your messages.
• They provide the foundational support for email authentication and give DMARC its power in enforcing your domain.

If you are serious about establishing a secure email infrastructure, you can’t overlook SPF and DKIM. These protocols are not just technical settings; they are business-critical safekeeping, protecting your revenue, your data, and your brand’s reputation.

Make sure your email domain is secure with SPF and DKIM. Check your email security now with Threatcop’s email spoof check.