SPF (Sender Policy Framework) works on the basis of TXT records, including IP addresses (IPv4 and IPv6 range) and mail servers allowed by domain owners to send emails on your behalf. However, email forwarding can cause SPF lookup failure as the SPF authentication process is based on the record of the primary domain, and forwarding breaks that cycle. Moreover, all of this makes way for a number of DNS lookups, leading to an SPF Permerror caused due to exceeding the limit of a maximum of 10 DNS lookups per record.

Why Email Forwarding Causes SPF Lookup Failure?

Emails experiencing SPF lookup failures are either marked as suspicious or rejected. Here’s what leads to this-

  • Change in Path

A forwarded email message navigates through a different path and mail server or service. SPF records are pertinent to specific domains, and if the forwarding servers don’t belong to the list of authorized servers of the original sender’s domain, it prompts an SPF lookup failure, causing an email deliverability problem.

  • Missing Forwarder’s IP in SPF Record

Since SPF records include all the IP addresses and mail servers allowed to send messages on behalf of organizations, SPF lookup failures are likely to occur with forwarding sending IPs if they aren’t listed. The recipients’ mail servers will experience mismatches, and the SPF system will fail for senders.

The SPF Lookup Limit Challenge

SPF operates perfectly with direct email delivery, however, problems arise when email forwarding is involved. This is because SPF authentication checks are performed on the forwarded email, which requires more SPF lookups for each step, ultimately adding to the limit. 

The concept of SPF lookup limit was brought up to prevent too many DNS lookups, which can otherwise degrade performance and potentially be exploited for malicious purposes. When these limits are reached, legitimate emails may be rejected or marked as suspicious, and malicious emails might bypass scrutiny.

Resolving the SPF Lookup Limit Issue

Here are actionable pointers that have proven to help domain administrators in fixing SPF lookup limit issues triggered by email forwarding-

  • Simplifying Forwarding Chains

Minimize the steps involved in the email forwarding process by consolidating forwarding rules and eliminating unnecessary hops. 

  • Using SPF Record Flattening

AutoSPF rewrites your SPF record to compress it by including all the authorized IP addresses and domains in a single record. The SPF flattening process eliminates the need for repeated SPF lookups.

  • Enabling DKIM and DMARC

DKIM and DMARC are advanced email authentication protocols. DKIM checks the sender’s authenticity by comparing public and private keys. DMARC, on the other hand, instructs recipients on how to deal with illegitimate emails coming from your domain. You can choose one of the three actions: none, quarantine, or reject.

  • Using Email Service Providers for Forwarding Solutions

Using a specialized email forwarding service to manage challenges helps mitigate SPF issues as it regulates your organization’s TXT record limit, validity, and correctness.

  • Contacting Email Provider

Reach out to your email provider or hosting service to discuss SPF lookup limit issues. They may be able to provide guidance or adjust the limits for your specific needs.

  • Regular Monitoring and Adjustments

Regularly monitor your email forwarding setup and adjust it as necessary. Keep an eye on email delivery reports and SPF failures to identify and address any ongoing issues.

Summary

Email forwarding can wreak havoc on SPF (Sender Policy Framework) records, leading to SPF lookup failures. These failures occur because email forwarding disrupts the SPF authentication process, causing an increase in SPF DNS lookups, eventually exceeding the limit. The DNS lookup limit exists to prevent excessive DNS queries that can harm performance or be exploited for malicious purposes. When limits are breached, legitimate emails may be rejected or flagged, while malicious ones can sneak through.

To tackle this issue, administrators can simplify forwarding chains, utilize SPF flattening to compress SPF records, enable DKIM and DMARC for enhanced email authentication, consider email forwarding services, contact email providers for guidance, and maintain regular monitoring and adjustments. Protect your emails from SPF lookup failures with these strategies.

Reach out to us today to get support in untangling the SPF management drill! Trust us, we are experts at doing that.