What deliverability benefits do I get from FCrDNS? How should I set up SPF records using Sparkpost?
Matthew Whittaker
Co-founder & CTO, Suped
Published 1 Jul 2025
Updated 16 Aug 2025
7 min read
Email deliverability relies on a complex interplay of technical configurations, all designed to build trust with mailbox providers. Two critical components that often come up in this conversation are FCrDNS, or Forward-Confirmed Reverse DNS, and the proper setup of SPF (Sender Policy Framework) records, especially when sending through an Email Service Provider (ESP) like SparkPost. Understanding how these elements contribute to your sending reputation can significantly impact whether your emails land in the inbox or the spam folder.
When an email server receives an incoming message, it performs a series of checks to verify the sender's authenticity. FCrDNS is one such check, where the receiving server looks up the IP address of the sending server to find its hostname (reverse DNS lookup), and then attempts to resolve that hostname back to the original IP address (forward DNS lookup). If both lookups match, it confirms the legitimacy of the sending server, adding a layer of trust.
Properly configured FCrDNS, alongside robust SPF records, are foundational to establishing a trustworthy sending identity. Ignoring these can lead to messages being flagged as suspicious, increasing the likelihood of them being rejected or routed to the junk folder. Let's delve into the specific deliverability benefits of FCrDNS and how to effectively set up SPF records with SparkPost.
Understanding FCrDNS and its deliverability impact
FCrDNS is essentially a two-way validation of your sending IP address. It confirms that the IP address sending your email corresponds to a specific domain and that this domain, in turn, maps back to that same IP. This verification is crucial because it helps to prevent email spoofing and makes it harder for malicious actors to impersonate legitimate senders. Many mailbox providers consider FCrDNS a prerequisite for good email deliverability.
The primary benefit of FCrDNS is enhanced trust and credibility. When a receiving server sees a valid FCrDNS, it signals that the sending server is legitimate and not part of a botnet or a spam operation. This reduces the chances of your emails being marked as spam or blocked. While it might seem like a small detail, it’s a foundational element in the larger email authentication landscape, working in concert with SPF, DKIM, and DMARC to build your sender reputation.
It is important to understand that FCrDNS is typically configured on the sending mail server's IP address. If you're using an ESP like SparkPost, they manage the FCrDNS for their sending infrastructure. While the FCrDNS hostname might not directly match your From: header domain, having a correctly configured FCrDNS (e.g., to a something.sparkpostmail.com hostname) is generally sufficient for most mailbox providers. For more information on FCrDNS, refer to our guide on reverse DNS and FCrDNS.
Configuring SPF records for SparkPost
SPF (Sender Policy Framework) is an email authentication method designed to prevent sender address forgery. It allows domain owners to publish a DNS record that specifies which mail servers are authorized to send email on behalf of their domain. When an email arrives, the recipient's server checks the SPF record to verify if the sending IP address is indeed permitted. A mismatch can lead to emails being rejected or marked as spam.
When using SparkPost, setting up your SPF record correctly is crucial for ensuring your emails are authenticated. SparkPost typically provides an include mechanism that you add to your domain's SPF record. This delegates the authority to SparkPost's servers to send mail on your behalf. This approach is generally straightforward and effective.
A typical SparkPost SPF record setup involves adding an include statement to your existing SPF record. If you don't have one, you'll create a new TXT record. Here's an example of how your SPF record might look, assuming it's the only sending service for your domain:
Example SPF record for SparkPostTXT
v=spf1 include:sparkpostmail.com ~all
For more detailed instructions, you can refer to SparkPost's own documentation on sending domain requirements. Keep in mind that SPF records can be complex, especially with multiple sending services. It is best practice to consolidate your SPF into a single record to avoid issues like too many DNS lookups.
Beyond basic SPF: alignment and shared infrastructure
Standard SPF setup
Most users rely on the default include:sparkpostmail.com mechanism. This is simple to implement and generally provides robust SPF authentication. It means that any IP address authorized by SparkPost is allowed to send on your behalf.
This setup is common for ESPs and works well for most use cases, providing flexibility for SparkPost to manage their sending IPs without requiring constant updates to your SPF record.
Dedicated IP considerations
If you have a dedicated IP address with SparkPost, you have the option to list those specific IPs in your SPF record instead of using the include mechanism. This provides tighter control over which IPs can send for your domain.
Manual updates: You will be responsible for updating your SPF record if SparkPost changes your dedicated IPs.
Increased control: Offers a higher level of specificity, potentially reducing concerns about other users on shared SparkPost infrastructure.
While the FCrDNS of SparkPost's sending IPs might not directly align with your From: header domain, this is a common practice with ESPs. The crucial aspect is that SparkPost has properly configured FCrDNS for its infrastructure. The focus for your domain's authentication should be on a strong SPF record that authorizes SparkPost, along with DKIM and DMARC. These three authentication methods provide comprehensive protection against spoofing and ensure your emails are trusted.
It is important to remember that SPF primarily applies to the Mail From (or bounce) domain, not necessarily the From: header domain that recipients see. For alignment with the From: header, DKIM and DMARC become even more critical. You can learn more about how SPF, DKIM, and DMARC affect deliverability.
Maximizing your email authentication and trust
Achieving excellent email deliverability is a multi-faceted endeavor that extends beyond just FCrDNS and SPF. While these are vital, a comprehensive strategy involves other key authentication protocols like DKIM and DMARC. DKIM provides a digital signature for your emails, ensuring that the content hasn't been tampered with in transit. DMARC, on the other hand, acts as a policy layer, telling receiving servers how to handle emails that fail SPF or DKIM checks, and providing valuable reports on your email traffic.
For the best email deliverability, especially with major mailbox providers like Google and Yahoo, it is increasingly important to have all three protocols correctly implemented and aligned. This holistic approach signals to receiving servers that you are a legitimate sender taking active steps to prevent abuse of your domain. You can also explore tutorials on setting up these records.
Furthermore, continuous monitoring of your email deliverability is key. Regularly check your DMARC reports to identify any authentication failures and understand their root cause. Staying off email blocklists (or blacklists) is also paramount, as an unexpected listing can severely impact your ability to reach the inbox. Tools that help you check blocklists can be invaluable.
In summary, while FCrDNS provides a foundational layer of trust at the IP level, and SPF verifies the legitimacy of sending servers, a truly robust email deliverability strategy involves aligning all your authentication protocols, managing your sending reputation, and actively monitoring your email program. This proactive approach helps ensure your messages consistently reach their intended recipients.
Views from the trenches
Best practices
Ensure FCrDNS is correctly set up for your sending IPs, as this builds fundamental trust for your mail server.
Verify that your SparkPost SPF record includes their official domains to authorize their sending on your behalf.
Implement DKIM and DMARC in addition to SPF to provide comprehensive email authentication and stronger domain protection.
Regularly monitor your DMARC reports for authentication failures and potential spoofing attempts on your domain.
Common pitfalls
Not having a valid FCrDNS record for your sending IPs, which can lead to increased spam filtering.
Misconfiguring your SPF record, such as exceeding the 10-lookup limit or including unauthorized senders.
Relying solely on SPF without implementing DKIM and DMARC, leaving your domain vulnerable to spoofing.
Failing to update SPF records when changing ESPs or adding new sending services, causing authentication failures.
Expert tips
For dedicated IPs, consider explicitly listing the IPs in your SPF record for tighter control, but remember the manual maintenance.
Be aware that SparkPost manages the FCrDNS for their shared IPs, and aligning it with your From domain isn't usually necessary.
Prioritize reducing the number of different domains in your email headers where possible to simplify spam filter evaluation.
If using an include mechanism, understand you're delegating authority and rely on your ESP's internal anti-abuse controls.
Expert view
Expert from Email Geeks says there is no extra deliverability benefit if the PTR record matches the sender's domain directly, as long as FCrDNS is already correctly established.
2022-12-12 - Email Geeks
Expert view
Expert from Email Geeks says that if you are using a reputable provider like SparkPost, there is no need to worry about shared infrastructure issues, as they have robust internal controls.
SparkPost. Understanding how these elements contribute to your sending reputation can significantly impact whether your emails land in the inbox or the spam folder.
Google and 
Yahoo, it is increasingly important to have all three protocols correctly implemented and aligned. This holistic approach signals to receiving servers that you are a legitimate sender taking active steps to prevent abuse of your domain. You can also explore tutorials on setting up these records.
