What are common misconceptions and best practices regarding SPF records and email deliverability for small mail servers?
Matthew Whittaker
Co-founder & CTO, Suped
Published 6 May 2025
Updated 19 Aug 2025
7 min read
When operating a small mail server, navigating the complexities of email deliverability can feel like a daunting task. While large email service providers (ESPs) handle many technical configurations behind the scenes, small server administrators bear the full responsibility for their setup.
Among the various authentication protocols, SPF (Sender Policy Framework) is often highlighted, yet it's frequently misunderstood, particularly in how it impacts smaller operations. It's not uncommon to encounter misconceptions that can lead to significant deliverability issues, rather than improvements.
I'll clarify common misunderstandings and outline best practices for SPF records, ensuring your emails from a small mail server reliably reach their intended inboxes.
Many small mail server operators believe that simply publishing an SPF record guarantees inbox placement. This is a common misconception. While SPF is a crucial authentication method, it's just one piece of a larger deliverability puzzle. SPF helps receiving mail servers verify that an email claiming to come from your domain was indeed sent by an IP address authorized by you, reducing spoofing. However, it doesn't account for other critical factors like sender reputation, content quality, or recipient engagement.
Another frequent misunderstanding revolves around the SPF all mechanism, specifically the difference between -all (fail) and ~all (softfail). Many assume -all is always the more secure and preferred option. However, for small mail servers, a strict fail policy can inadvertently cause legitimate emails to be rejected if there's any misconfiguration or if a new sending source isn't immediately added to the SPF record. The article by Spam Resource explains the implications of SPF policies.
There's also the notion that major mailbox providers like Gmail and Outlook unfairly penalize small independent senders, regardless of their SPF setup. While large providers do have sophisticated filtering systems, they are designed to combat spam effectively, not to specifically target small servers. A well-configured SPF record, combined with other authentication methods, is essential for all senders, regardless of size, to establish trust and ensure email deliverability.
Setting up SPF effectively
For small mail servers, setting up SPF correctly is crucial for building sender reputation and improving deliverability. Your SPF record specifies which mail servers are authorized to send email on behalf of your domain. A proper setup helps prevent your domain from being used for email spoofing, which is a common tactic for phishing and spam.
The core of your SPF record should include all IP addresses or hostnames of servers that send email for your domain. This includes your primary mail server, any web servers sending transactional emails, or third-party services you use, such as marketing platforms or CRM systems. For a detailed guide on setting up, refer to a comprehensive SPF guide. Remember, exceeding the 10 DNS lookup limit is a common pitfall that can break your SPF, causing deliverability issues.
Here's an example of a simple SPF record for a small mail server, where yourdomain.com is your domain and 192.0.2.1 is your server's IP address. Always use -all to explicitly state that only listed IPs are authorized, preventing others from sending on your behalf. If you need to troubleshoot intermittent delivery failures due to SPF, this strict policy is key.
Ensure your SPF record is published as a TXT record in your domain's DNS. Tools can help you verify your SPF record for proper DNS configuration. This verification step is critical, as a malformed record can do more harm than good.
Beyond SPF: a holistic approach
While SPF is foundational, it's not a standalone solution for email deliverability. For small mail servers, integrating SPF with DKIM (DomainKeys Identified Mail) and DMARC (Domain-based Message Authentication, Reporting, and Conformance) is crucial. These three protocols work in tandem to provide robust email authentication. Setting up all three authentication protocols significantly boosts your domain's trustworthiness.
DKIM adds a digital signature to your emails, verifying that the email content hasn't been tampered with in transit. DMARC, on the other hand, builds upon SPF and DKIM by allowing domain owners to tell receiving mail servers what to do with emails that fail authentication. This policy can range from monitoring (p=none) to quarantining (p=quarantine) or rejecting (p=reject) such emails. Implementing DMARC with a monitoring policy first is a best practice to observe your email flow and identify any legitimate sending sources that might be failing authentication before enforcing stricter policies.
Beyond authentication, maintaining a good sending reputation is paramount. This involves consistently sending high-quality, relevant emails to engaged recipients. Avoiding spam traps, managing bounce rates, and promptly removing inactive addresses from your mailing lists are vital steps. For further reading, explore why your emails might be going to spam and how to fix it.
Maintaining SPF and monitoring
Regular monitoring and maintenance of your SPF records are essential, especially for small mail servers that might have fluctuating sending requirements. New services, server changes, or even updates from your hosting provider can inadvertently break your SPF record or introduce unauthorized senders. This oversight can quickly lead to emails being rejected or flagged as spam, negating all your efforts in proper setup.
Keep a close eye on your DMARC reports, as they provide invaluable insights into SPF and DKIM authentication results. These reports will show you which sending sources are passing or failing authentication, allowing you to identify any unauthorized senders or misconfigurations. Addressing these issues promptly is key to maintaining a healthy sender reputation. You can also monitor whether your domain appears on any email blocklists (or blacklists), which can severely impact your deliverability.
Consider implementing an SPF flattening solution if your record approaches the 10 DNS lookup limit. This can prevent intermittent failures that are difficult to diagnose. Regularly review your authorized sending sources and update your SPF record as needed. Proactive management is a hallmark of successful email deliverability for any mail server, big or small.
The risk of ignoring DNS lookup limits
Exceeding the 10-DNS-lookup limit in your SPF record leads to a PermError, causing receivers to treat your email as unauthenticated, regardless of its legitimacy. This can severely impact deliverability.
For small mail servers, it's easy to hit this limit with multiple include mechanisms from various third-party services. Being proactive in managing this is vital for ensuring your email reaches the inbox.
Views from the trenches
Best practices
Always include all legitimate sending IPs and services in your SPF record.
Use '-all' as your SPF policy to enforce strict authentication once confident in your setup.
Combine SPF with DKIM and DMARC for comprehensive email authentication.
Common pitfalls
Exceeding the 10 DNS lookup limit in your SPF record, leading to PermErrors.
Using a '?all' policy indefinitely, which allows unauthorized emails to pass SPF checks.
Failing to update your SPF record when adding or removing sending services.
Expert tips
If you move your mail server, even if it's a small VPS, Google typically doesn't immediately send mail to spam if other authentication is correct.
For small senders, the challenge isn't unfairness from big providers, but often misconfigurations or lack of full authentication.
Don't fall for advice recommending actively harmful SPF records like 'v=spf1 ipv4: ipv6: -all' or similar useless policies.
Expert view
Expert from Email Geeks says they rarely have trouble getting through to Gmail with their small, independent server, even on a VPS and not publishing '-all'.
2020-01-24 - Email Geeks
Marketer view
Marketer from Email Geeks says they moved their small mail server around, and Google did not send their mail to bulk at all, contradicting the idea that large providers penalize small independent senders.
2020-01-24 - Email Geeks
Key takeaways for small mail servers
For small mail servers, mastering SPF records is a critical step towards achieving reliable email deliverability. It's not just about having an SPF record, but ensuring it's accurately configured, regularly updated, and integrated within a broader email authentication strategy that includes DKIM and DMARC.
By understanding and avoiding common misconceptions, such as the dangers of exceeding the DNS lookup limit or misinterpreting SPF policies, you can significantly improve your email's chances of reaching the inbox. Proactive management of your domain's authentication and reputation will safeguard your communication and build trust with recipients, regardless of your server's size.
Gmail and 
Outlook unfairly penalize small independent senders, regardless of their SPF setup. While large providers do have sophisticated filtering systems, they are designed to combat spam effectively, not to specifically target small servers. A well-configured SPF record, combined with other authentication methods, is essential for all senders, regardless of size, to establish trust and ensure email deliverability.
