Sender Policy Framework (SPF) flattening is crucial for managing email authentication and ensuring deliverability. However, if your SPF flattening service stops working, it can disrupt your email infrastructure, potentially leading to email rejection, spoofing risks, or compliance issues.
In this guide, we’ll explore practical steps to troubleshoot and resolve SPF flattening failures, including analyzing DNS errors, optimizing SPF records, and leveraging automated solutions.
1. Identify the Root Cause
Before making changes, diagnose the problem by checking for common SPF flattening issues:
A. DNS Lookup Failures
SPF records have a 10 DNS lookup limit. If your flattening service isn’t working, your SPF record may exceed this limit, leading to a "Too many DNS lookups" error.
B. Expired or Misconfigured Flattening Service
If you're using a third-party SPF flattening service, verify its status. An expired subscription, API failure, or incorrect configuration can cause failures.
C. Syntax Errors in SPF Record
A malformed SPF record can invalidate email authentication. Use an SPF checker to validate the syntax.
nslookup -type=txt yourdomain.com
If the SPF record contains unexpected characters or errors, fix them immediately.
D. DNS Propagation Delays
If you've recently updated your SPF record, DNS changes may take time to propagate. Use the following command to verify DNS changes:
dig txt yourdomain.com
2. Manually Flatten Your SPF Record
If your automatic SPF flattening service stops working, you can flatten it manually by resolving "include" mechanisms into IP addresses.
Step 1: Extract IP Addresses from Include Mechanisms
Use an SPF lookup tool to get the list of IP addresses referenced by "include" mechanisms.
Example SPF record:
v=spf1 include:_spf.google.com include:_spf.example.com ~all
Resolve the "include" entries:
dig txt _spf.google.com dig txt _spf.example.com
Step 2: Replace Includes with IPs
Manually flatten your SPF record by replacing includes with resolved IPs:
v=spf1 ip4:192.168.1.1 ip4:203.0.113.5 ip6:2001:db8::1 ~all
Step 3: Publish the Flattened SPF Record
Update your DNS settings to include the new SPF record.
3. Use an Automated SPF Flattening Tool
If your SPF flattening service is unreliable, consider using alternative automation tools to simplify SPF record management.
Example Code to Automate SPF Flattening
If you want to flatten SPF records dynamically, you can use Python with dnspython:
import dns.resolver def resolve_spf(domain): try: answers = dns.resolver.resolve(domain, 'TXT') for rdata in answers: for txt_string in rdata.strings: if txt_string.decode().startswith("v=spf1"): return txt_string.decode() except Exception as e: print(f"Error resolving {domain}: {e}") return None domain = "yourdomain.com" spf_record = resolve_spf(domain) print(f"Resolved SPF Record: {spf_record}")
This script fetches SPF records and resolves includes.
4. Split SPF Records to Stay Within DNS Limits
If flattening still exceeds 10 lookups, consider splitting your SPF records across multiple subdomains.
Example of Split SPF Records
Main SPF record:
v=spf1 include:spf1.yourdomain.com include:spf2.yourdomain.com ~all
Subdomain SPF records:
spf1.yourdomain.com TXT "v=spf1 ip4:192.168.1.1 ip4:203.0.113.5 ~all" spf2.yourdomain.com TXT "v=spf1 ip6:2001:db8::1 ~all"
5. Monitor and Validate SPF Regularly
Use automated monitoring to detect SPF failures before they impact email deliverability.
SPF Monitoring with Python
import smtplib def test_email_delivery(): try: server = smtplib.SMTP('smtp.yourdomain.com', 587) server.starttls() server.login("your-email@yourdomain.com", "password") server.sendmail("from@yourdomain.com", "to@example.com", "Test SPF Email") print("Email sent successfully!") server.quit() except Exception as e: print(f"Email sending failed: {e}") test_email_delivery()
Conclusion
If your SPF flattening service stops working, immediate troubleshooting is essential to avoid email authentication failures. By manually flattening SPF, using automated tools, and monitoring SPF health, you can maintain reliable email deliverability.
If you need an automated SPF solution, consider integrating YourDMARC to simplify SPF management and ensure compliance.
Need help with SPF and email security? Contact us today!
