To resolve the MXToolbox SPF record DNS lookup limit exceeded error, a multi-faceted approach is required. The SPF specification (RFC 7208) limits DNS lookups to 10 to prevent DDoS attacks. Minimizing 'include' mechanisms is key. This involves auditing and removing unnecessary 'include' statements, replacing 'include' statements with direct IP addresses (SPF flattening), and utilizing subdomains for different email streams with separate SPF records. For services like HubSpot and Sendgrid, examine the 5321.from address for proper configuration. It's crucial to authorize only necessary domains and be wary of bad advice from ESPs. Maintenance is required with SPF flattening, and remember that the DNS query count matters, not just the domain count.

To resolve the MXToolbox SPF record DNS lookup limit exceeded error, several strategies are recommended. The primary approaches include reducing the number of 'include' statements in the SPF record, which can be achieved by removing unnecessary or redundant includes, flattening the SPF record by replacing 'include' statements with direct IP addresses, and utilizing subdomains for different email sending services, each with its own SPF record. It's also crucial to use as few includes as possible, ensuring that only domains actively sending email on your behalf are included, and to be aware of the potential maintenance overhead of flattening SPF records due to IP address changes.

To address the MXToolbox SPF record DNS lookup limit exceeded error, experts recommend several key strategies. Primarily, it's crucial to reduce the number of 'include' statements in your SPF record by auditing and removing unnecessary entries, as excessive use of 'include:' is a common mistake. For HubSpot and Sendgrid, check the 5321.from address to determine if they can be removed or if a specific record for that domain is needed instead of the base domain. Avoid publishing SPF records for domains other than those in the 5322.from. Using subdomains for different email types (e.g., marketing vs. transactional) can also help manage reputation and control, and potentially limit SPF lookups on the root domain.

Documentation across various sources indicates that the MXToolbox SPF record DNS lookup limit exceeded error arises because the SPF specification (RFC 7208) restricts the number of DNS lookups to a maximum of 10 per SPF check to prevent denial-of-service attacks and ensure email delivery efficiency. To resolve this, the primary recommendation is to reduce the number of 'include' mechanisms and nested lookups in the SPF record. This can be achieved by ensuring that only actively used sending providers are included and by considering the use of subdomains to distribute SPF records, thus reducing the lookup load on the primary domain.