Why TTL of DKIM records matters
When an email is sent, the recipient's antispam system performs DNS lookups to validate SPF and DKIM records.
If the TTL of these DNS records is set too low, the receiving system may need to perform frequent DNS queries to refresh the record.
This can introduce delays or failures in the validation process, particularly if the DNS server is slow to respond or experiences downtime.
Although SPF records with a TTL of 5 minutes are accepted by both Outlook/Hotmail/MSN (Microsoft) and Google and Yahoo, this is not the case for DKIM.
Google and Yahoo accept DKIM records with a TTL of 5 minutes, whereas Outlook/Hotmail/MSN (Microsoft) do not accept DKIM keys with a TTL of 5 minutes :
Best Practices for Optimizing Email Deliverability
To maximize email delivery success across all major platforms, it is advisable to configure DNS records with a more conservative TTL. Specifically:
- Set a Minimum TTL of 60 Minutes: This provides a balance between ensuring updated records and minimizing the risk of validation failures due to frequent DNS lookups.
- Monitor DKIM Validation Across Platforms: Use email testing tools like ours to verify that your DKIM signature is recognized as valid by major email providers.
- Ensure Reliable DNS Performance: Work with a robust DNS provider to reduce lookup delays and improve overall reliability.
Conclusion
The discrepancies in DKIM validation between Microsoft and other email providers like Google and Yahoo underscore the critical role of DNS TTL settings. While low TTL values may seem advantageous for rapid updates, they can inadvertently cause email deliverability issues. By adhering to a TTL of at least 60 minutes, you can enhance your email's chances of bypassing spam filters and reaching the recipient's inbox without delivery issues.