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Every 39 seconds, a cyberattack occurs across the globe, most of which may be perpetrated through email. SPF helps authorize your senders so that your domain cannot be manhandled by an unauthorized third party email sender. To set up SPF is the DNS, you must first know what is SPF record in DNS

SPF or Sender Policy Framework is an email authentication protocol that allows only specific IPs to send emails using a domain name. Any IP address outside the list will not reach the receiver’s mailbox as it leads to SPF failure.

It protects your email domains from hackers to steer clear of phishing, spamming, and email spoofing attacks. Email authentication techniques like SPF are ideal for keeping your email domain protected. Its structure has 3 main components; mechanism, modifiers, and qualifiers. 

This blog will discuss what is SPF record in DNS and more. 

What is an SPF record in DNS?

SPF is short for Sender Policy Framework, a DNS TXT record with a list of servers allowed to send emails from a certain domain. It works when domain owners update arbitrary texts into DNS or Domain Name System to track and regulate respective domain names. 

To understand the DNS SPF record, let’s quickly see what DNS is.

It’s a system that translates a computer’s host name into an IP address on the internet. All the internet-enabled devices have their IP addresses, which help other devices to locate them. 

Now, let’s come back to the main question, what’s an SPF record?.’ Say, if your business uses various sending IPs, you can use PowerDMARC’s free SPF record generator to create an inventory of authorized IPs in the form of a TXT document called SPF record to authenticate genuine IPs allowed to use your domain name. 

How do SPF Records Work?

So far, we’ve discussed what is SPF record in DNS, now it’s time to understand how it works. The authentication process starts after you generate an SPF record for your domain. The return path email address is cross-checked at the receiver’s end. A return-path email address is set in the email header, which defines how to handle bounced emails. It verifies whether or not the sending email address is lodged in the SPF records.

If the approval is positive, emails are sent to ‘inbox’; otherwise, it may lead to SPF failure

SPF Record Structure and Components

DNS SPF record makes your domain credible, trustworthy, and , consequently upholds your company’s image. There’s a proper SPF record structure that helps in maintaining it easily. SPF records have a TXT record type, which is a single string of text. 

A DNS SPF record starts with the ‘v=’ element, indicating the version used. ‘SPF1’ is the most common version understood by mail exchanges. The following terms determine mechanisms for verifying whether or not a domain can send emails. 

Mechanisms

Here are the eight mechanisms

  1. ALL: It always matches. This shows default results like ‘-all’ for unmatching IPs.
  2. A: Domain name with A or AAAA address record matches as they can be resolved to the sender’s address.
  3. IP4: The match is successful when the sender is linked to the given IPv4 address range.
  4. IP6: The match is successful if the sender belongs to the given IPv6 address range.
  5. MX: Sender’s email address is authorized when their domain name consists of an MX record for resolution.
  6. PTR: The match is validated when the PTR record is linked to a given domain resolving to the client’s address. It’s not suggested as it may block all emails sent using your domain.
  7. EXISTS: It works if the given domain name is validated. This SPF mechanism functions with all resolved addresses. 
  8. INCLUDE: It references other domain policies. So, if that passes, it passes automatically. However, if the included policy fails, processing continues. 

Modifiers

Modifiers decide the DNS SPF record’s working parameters. It consists of name or value pairs separated by the ‘=’ symbol, pointing out additional information. They’re witnessed several times at the end of the SPF record, and all the unrecognized modifiers are ignored in the process.

The ‘redirect’ modifier directs to other SPF records responsible for efficient functioning. Experts use them whenever more than one domain is linked to the same SPF record. This modifier has to be used if a single entity controls all the domains, otherwise ‘include’ modifier is used.

Qualifiers

Each mechanism can be combined with one of four qualifiers.

‘+’  for PASS result

‘?’  for a NEUTRAL result interpreted like NONE policy.

‘~’ for SOFTFAIL. Usually, messages that return a SOFTFAIL are accepted but tagged.

‘-’ for FAIL, the email is rejected.

Why are SPF Records Used?

The following are the primary reasons for knowing what is SPF record in DNS and its usage. 

Averting Cyberattacks

Malicious actors send unauthenticated and fraudulent emails using your domain name to gain the trust of your clients, prospects, stakeholders, etc. They create business email addresses using your domain for attempting phishing, spamming, email spoofing, and other cyberattacks. 

However, if you understand the configuration process for the protocol and create one for your company, it’ll be relatively challenging and time-consuming for threat actors to exploit your domain. This will eventually reduce the probability of coming under their radar.

Improving Email Deliverability

Domains without DNS SPF records have high chances of their emails being bounced back or labeled as ‘spam.’ If this persists, the ability to reach the mailbox will be hurt. This means that most emails sent using your domain name will fail to reach the receiver’s end, impacting your business. 

DMARC Compliance

DMARC stands for Domain-based Message Authentication, Reporting, and Conformance. It’s another email authentication technique that prevents spamming, phishing, and email spoofing. 

It ensures that only permitted entities can send emails through a specific domain. It’s based on SPF and DKIM (another email authentication policy) verification and directs a receiver’s mailbox on how to treat each email received from your domain. Based on this, they’re marked as ‘spam,’ ‘rejected,’ or ‘delivered as normal.’ 

Moreover, domain administrators can check reports registering their email activity and alter their DMARC policy accordingly. PowerDMARC can make it hassle-free for your business to adopt the DMARC policy by regularly monitoring and adjusting it as per the requirement. 

Final Thoughts

SPF-protected email domains repel bad actors as it takes extra time and effort to compromise them to attempt malicious activities. SPF synchronizes with DNS to ensure only authorized entities can send emails from a particular domain. 

Otherwise, cyberactors can exploit your brand name by sending fraudulent and spam emails, asking receivers to click a malicious link, download a corrupted file, or share sensitive details. In many cases, they even request for direct money transfer in your business’s name. 

Once you’re all set up with your DNS record for SPF, don’t forget to check it using our free SPF checker tool to test its validity!

A very common problem that SPF users face on a daily basis is the risk of generating too many DNS lookups that can make them easily exceed the SPF hard limit. This returns an SPF PermError result when DMARC monitoring is enabled and causes email deliverability issues. With industry experts coming up with solutions like SPF flattening services to mitigate this issue, PowerSPF actually delivers its claims and exceeds expectations. Read on to learn how!

Too Many DNS Lookups: Why Does This Happen?

The first thing you should understand is why you end up generating too many DNS lookups in the first place. This is because, no matter what email exchanger solution you use, your service provider adds more mechanisms to your record resulting in more lookups.

For example, if you use Google’s email exchanger, or Gmail, an SPF record like v=spf1 include:[email protected] -all actually generates a total of 4 DNS lookups. Nested includes also initiate more lookups and if you use several third-party vendors to send emails using your domain, you can easily exceed the 10 DNS lookup limit.

Is SPF Flattening the Solution? No!

The answer is no. SPF manual flattening can help you stay under the SPF 10 lookup limit, but it has its own set of limitations and challenges. If you flatten your SPF manually, it is simply replacing the include statements in your SPF record with their corresponding IP addresses to eliminate the need for lookups. This ensures that you don’t end up generating too many DNS lookups in the first place, thereby helping you stay under the 10 lookup SPF limit and avoid permerror . But problems with manual SPF flattening solutions are:

  • The SPF record length can be too long (more than 255 characters)
  • Your email service provider can change or add to their IP addresses without notifying you
  • There is no dashboard to monitor email flow, change or update your domains and mechanisms, and track activities
  • You need to constantly make changes to your DNS to update your SPF record
  • Your email deliverability might be impacted due to the frequent IP changes

How do these affect you? Well, if your SPF record isn’t updated on the new IP addresses your email service providers are using, every now and then when these IP addresses are used your emails will inevitably fail SPF on the receiver’s side. 

Dynamic SPF Flattening to Resolve Too Many DNS Lookups

A smarter solution to bid adieu to DNS lookups error is PowerSPF, your automatic SPF record flattener. PowerSPF is your real-time SPF flattening solution that helps you:

  • Easily configure SPF for your domain with just a few clicks
  • One-click instant SPF record flattening with a single include statement to enjoy automatic SPF include management
  • Always stay under the 10 DNS lookup limit
  • Auto-update netblock and scan for changed IP addresses constantly to keep your SPF record up-to-date
  • Maintain a user-friendly dashboard wherein you can easily update changes to your policies, add domains and mechanisms, and monitor email flow.

Why rely on SPF compression tools that can provide temporary results with underlying limitations? Optimize your SPF Record and mitigate the SPF hard limit with  Automatic SPF today! Sign up for PowerSPF now?

Reasons why to avoid SPF Flattening

Sender Policy Framework, or SPF is a widely acclaimed email authentication protocol that validates your messages by authenticating them against all the authorized IP addresses registered for your domain in your SPF record. In order to validate emails, SPF specifies to the receiving mail server to perform DNS queries to check for authorized IPs, resulting in DNS lookups.

Your SPF record exists as a DNS TXT record that is formed of an assemblage of various mechanisms. Most of these mechanisms (such as include, a, mx, redirect, exists, ptr) generate DNS lookups. However, the maximum number of DNS lookups for SPF authentication is limited to 10. If you are using various third-party vendors to send emails using your domain, you can easily exceed the SPF hard limit.

You might be wondering, what happens if you exceed this limit? Exceeding the 10 DNS lookup limit will lead to SPF failure and invalidate even legitimate messages sent from your domain. In such cases the receiving mail server returns an SPF PermError report to your domain if you have DMARC monitoring enabled.This makes us come to the primary topic of discussion for this blog: SPF flattening.

What is SPF Flattening?

SPF record flattening is one of the popular methods used by industry experts to optimize your SPF record and avoid exceeding the SPF hard limit. The procedure for SPF flattening is quite simple. Flattening your SPF record is the process of replacing all include mechanisms with their respective IP addresses to eliminate the need for performing DNS lookups.

For example, if your SPF record initially looked something like this:

v=spf1 include:spf.domain.com -all

A flattened SPF record will look something like this:

v=spf1 ip4:168.191.1.1 ip6:3a02:8c7:aaca:645::1 -all

This flattened record generates only one DNS lookup, instead of performing multiple lookups. Reducing the number of DNS queries performed by the receiving server during email authentication does help in staying under the 10 DNS lookup limit, however, it has problems of its own.

The Problem with SPF Flattening

Apart from the fact that your manually flattened SPF record may get too lengthy to publish on your domain’s DNS (exceeding the 255 character limit), you have to take into account that your email service provider may change or add to their IP addresses without notifying you as the user. Every now and then when your provider makes changes to their infrastructure, these alterations would not be reflected in your SPF record. Hence, whenever these changed or new IP addresses are used by your mail server, the email fails SPF on the receiver’s side.

PowerSPF: Your Dynamic SPF Record Generator

The ultimate goal of PowerDMARC was to come up with a solution that can prevent domain owners from hitting the 10 DNS lookup limit, as well as optimize your SPF record to always stay updated on the latest IP addresses your email service providers are using. PowerSPF is your automated SPF flattening solution that pulls through your SPF record to generate a single include statement. PowerSPF helps you:

  • Add or remove IPs and mechanisms with ease
  • Auto update netblocks to make sure your authorized IPs are always up-to-date
  • Stay under the 10 DNS lookup limit with ease
  • Get an optimized SPF record with a single click
  • Permanently defeat ‘permerror’
  • Implement error free SPF

Sign up with PowerDMARC today to ensure enhanced email deliverability and authentication, all while staying under the 10 DNS SPF lookup limit.

In this article, we will explore how to optimize SPF record easily for your domain. For enterprises as well as small businesses who are in possession of an email domain for sending and receiving messages among their clients, partners and employees, it is highly probable that an SPF record exists by default, which has been set up by your inbox service provider. No matter if you have a pre-existent SPF record or you need to create a new one, you need to optimize your SPF record correctly for your domain in order to ensure that it causes no email delivery issues.

Some email recipients strictly require SPF, which indicates that if you do not have an SPF record published for your domain your emails may be marked as spam in your receiver’s inbox. Moreover, SPF helps in detecting unauthorized sources sending emails on behalf of your domain.

Let us first understand what is SPF and why do you need it?

Sender Policy Framework (SPF)

SPF is essentially a standard email authentication protocol that specifies the IP addresses that are authorized to send emails from your domain. It operates by comparing sender addresses against the list of authorized sending hosts and IP addresses for a specific domain that is published in the DNS for that domain.

SPF, along with DMARC (Domain-based Message Authentication, Reporting and Conformance) is designed to detect forged sender addresses during email delivery and prevent spoofing attacks, phishing, and email scams.

It is important to know that although the default SPF integrated into your domain by your hosting provider ensures that emails sent from your domain are authenticated against SPF if you have multiple third-party vendors to send emails from your domain, this pre-existent SPF record needs to be tailored and modified to suit your requirements. How can you do that? Let’s explore two of the most common ways:

  • Creating a brand new SPF record
  • Optimizing an existing SPF record

Instructions on How to Optimize SPF Record

Create a Brand New SPF Record

Creating an SPF record is simply publishing a TXT record in your domain’s DNS to configure SPF for your domain. This is a mandatory step that comes before you start on how to optimize SPF record. If you are just starting out with authentication and unsure about the syntax, you can use our free online SPF record generator to create an SPF record for your domain.

An SPF record entry with a correct syntax will look something like this:

v=spf1  ip4:38.146.237 include:example.com -all

v=spf1Specifies the version of SPF being used
ip4/ip6This mechanism specifies the valid IP addresses that are authorized to send emails from your domain.
includeThis mechanism tells the receiving servers to include the values for the SPF record of the specified domain.
-allThis mechanism specifies that emails that are not SPF compliant would be rejected. This is the recommended tag you can use while publishing your SPF record. However it can be replaced with ~ for SPF Soft Fail (non-compliant emails would be marked as soft fail but would still be accepted) Or + which specifies that any and every server would be allowed to send emails on behalf of your domain, which is strongly discouraged.

If you already have SPF configured for your domain, you can also use our free SPF record checker to lookup and validate your SPF record and detect issues.

Common Challenges and Errors while Configuring SPF

1) 10 DNS Lookup limit 

The most common challenge faced by domain owners while configuring and adopting SPF authentication protocol for their domain, is that SPF comes with a limit on the number of DNS lookups, which cannot exceed 10. For domains relying on multiple third-party vendors, the 10 DNS lookup limit exceeds easily which in turn breaks SPF and returns an SPF PermError. The receiving server in such cases automatically invalidates your SPF record and blocks it.

Mechanisms that initiate DNS lookups: MX, A, INCLUDE, REDIRECT modifier

2) SPF Void Lookup 

Void lookups refer to DNS lookups which either return NOERROR response or NXDOMAIN response (void answer). While implementing SPF it is recommended to ensure DNS lookups do not return a void answer in the first place.

3) SPF Recursive loop

This error indicates that the SPF record for your specified domain contains recursive issues with one or more of the INCLUDE mechanisms. This takes place when one of the domains specified in the INCLUDE tag contains a domain whose SPF record contains the INCLUDE tag of the original domain. This leads to a never-ending loop causing email servers to continuously perform DNS lookups for the SPF records. This ultimately leads to exceeding the 10 DNS lookup limit, resulting in emails failing SPF.

4) Syntax Errors 

An SPF record may exist in your domain’s DNS, but it is of no use if it contains syntax errors. If your SPF TXT record contains unnecessary white spaces while typing the domain name or mechanism name, the string preceding the extra space would be completely ignored by the receiving server while performing a lookup, thereby invalidating the SPF record.

5) Multiple SPF records for the same domain

A single domain can have only one SPF TXT entry in the DNS. If your domain contains more than one SPF record, the receiving server invalidates all of them, causing emails to fail SPF.

6) Length of the SPF record 

The maximum length of a SPF record in the DNS is limited to 255 characters. However, this limit can be exceeded and a TXT record for SPF can contain multiple strings concatenated together, but not beyond a limit of 512 characters, to fit the DNS query response (according to RFC 4408). Though this was later revised, recipients relying on older DNS versions would not be able to validate emails sent from domains containing a lengthy SPF record.

Optimizing your SPF Record

In order to promptly modify your SPF record you can use the following SPF best practices:

  • Try typing down your email sources in decreasing order of importance from left to right in your SPF record
  • Remove obsolete email sources from your DNS
  • Use IP4/IP6 mechanisms instead of A and MX
  • Keep your number of INCLUDE mechanisms as low as possible and avoid nested includes
  • Do not publish more than one SPF record for the same domain in your DNS
  • Make sure your SPF record doesn’t contain any redundant white spaces or syntax errors

Note: SPF flattening is not recommended since it isn’t a one-time deal. If your email service provider changes their infrastructure, you’re going to have to change your SPF records accordingly, every single time.

Optimizing Your SPF Record Made Easy with PowerSPF

You can go ahead and try implementing all those above-mentioned modifications to optimize your SPF record manually, or you can forget the hassle and rely on our dynamic PowerSPF to do all that for you automatically! PowerSPF helps you optimize your SPF record with a single click, wherein you can:

  • Add or remove sending sources with ease
  • Update records easily without having to manually make changes to your DNS
  • Get an optimized auto SPF record with the single click of a button
  • Stay under the 10 DNS lookup limit at all time
  • Successfully mitigate PermError
  • Forget about SPF record syntax errors and configuration issues
  • We take away the burden of resolving SPF limitations on your behalf

Sign up with PowerDMARC today to bid adieu to SPF limitations forever!  

As a DMARC services provider, we get asked this question a lot: “If DMARC just uses SPF and DKIM authentication, why should we bother with DMARC? Isn’t that just unnecessary?”

On the surface it might seem to make little difference, but the reality is very different. DMARC isn’t just a combination of SPF and DKIM technologies, it’s an entirely new protocol by itself. It has several features that make it one of the most advanced email authentication standards in the world, and an absolute necessity for businesses.

But wait a minute. We’ve not answered exactly why you need DMARC. What does it offer that SPF and DKIM don’t? Well, that’s a rather long answer; too long for just one blog post. So let’s split it up and talk about SPF first. In case you’re not familiar with it, here’s a quick intro.

What is SPF?

SPF, or Sender Policy Framework, is an email authentication protocol that protects the email receiver from spoofed emails. It’s essentially a list of all IP addresses authorized to send email through your (the domain owner) channels. When the receiving server sees a message from your domain, it checks your SPF record that’s published on your DNS. If the sender’s IP is in this ‘list’, the email gets delivered. If not, the server rejects the email.

As you can see, SPF does a pretty good job keeping out a lot of unsavoury emails that could harm your device or compromise your organisation’s security systems. But SPF isn’t nearly as good as some people might think. That’s because it has some very major drawbacks. Let’s talk about some of these problems.

Limitations of SPF

SPF records don’t apply to the From address

Emails have multiple addresses to identify their sender: the From address that you normally see, and the Return Path address that’s hidden and require one or two clicks to view. With SPF enabled, the receiving email server looks at the Return Path and checks the SPF records of the domain from that address.

The problem here is that attackers can exploit this by using a fake domain in their Return Path address and a legitimate (or legitimate-looking) email address in the From section. Even if the receiver were to check the sender’s email ID, they’d see the From address first, and typically don’t bother to check the Return Path. In fact, most people aren’t even aware there is such a thing as Return Path address.

SPF can be quite easily circumvented by using this simple trick, and it leaves even domains secured with SPF largely vulnerable.

SPF records have a DNS lookup limit

SPF records contain a list of all the IP addresses authorized by the domain owner to send emails. However, they have a crucial drawback. The receiving server needs to check the record to see if the sender is authorized, and to reduce the load on the server, SPF records have a limit of 10 DNS lookups.

This means that if your organization uses multiple third party vendors who send emails through your domain, the SPF record can end up overshooting that limit. Unless properly optimized (which isn’t easy to do yourself), SPF records will have a very restrictive limit. When you exceed this limit, the SPF implementation is considered invalid and your email fails SPF. This could potentially harm your email delivery rates.

 

SPF doesn’t always work when the email is forwarded

SPF has another critical failure point that can harm your email deliverability. When you’ve implemented SPF on your domain and someone forwards your email, the forwarded email can get rejected due to your SPF policy.

That’s because the forwarded message has changed the email’s recipient, but the email sender’s address stays the same. This becomes a problem because the message contains the original sender’s From address but the receiving server is seeing a different IP. The IP address of the forwarding email server isn’t included within the SPF record of original sender’s domain. This could result in the email being rejected by the receiving server.

How does DMARC solve these issues?

DMARC uses a combination of SPF and DKIM to authenticate email. An email needs to pass either SPF or DKIM to pass DMARC and be delivered successfully. And it also adds one key feature that makes it far more effective than SPF or DKIM alone: Reporting.

With DMARC reporting, you get daily feedback on the status of your email channels. This includes information about your DMARC alignment, data on emails that failed authentication, and details about potential spoofing attempts.

If you’re wondering about what you can do to not get spoofed, check out our handy guide on the top 5 ways to avoid email spoofing.