When is SPF flattening necessary for email authentication?
Summary
What email marketers say13Marketer opinions
Email marketer from MailerLite clarifies that a poorly configured SPF record (e.g., exceeding lookup limits) can negatively impact email deliverability. SPF flattening can help maintain deliverability by simplifying the record.
Email marketer from DNSimple advises to review and flatten your SPF record proactively if you add or remove email sending services. This ensures the record remains optimized and compliant with the DNS lookup limit.
Email marketer from MXToolbox highlights that if tools like MXToolbox show that your SPF record exceeds 10 lookups, SPF flattening becomes necessary to ensure email deliverability.
Marketer from Email Geeks suggests putting the universal SPF string in front of the original SPF policy to automatically protect the policy from too many DNS lookups and other potential errors.
Email marketer from Mailhardener shares that SPF flattening helps to stay within the 10 DNS lookup limit, ensuring that emails don't fail SPF checks due to exceeding this limit. This is particularly useful when using multiple email service providers.
Marketer from Email Geeks explains that SPF flattening is necessary if you're exceeding 10 DNS lookups. They also suggest monitoring DMARC aggregate reports before making any decisions with SPF flattening solutions, as many people get SPF wrong and have unnecessary includes that can be omitted.
Email marketer from StackExchange notes that SPF flattening is important when the complexity of your SPF record (due to multiple includes) starts causing authentication failures because of exceeding the DNS lookup limit.
Email marketer from GlockApps shares that SPF flattening is required when your domain’s SPF record contains too many nested DNS lookups (more than 10). It simplifies the SPF record, preventing deliverability issues.
Email marketer from Email on Acid points out that using numerous third-party email marketing platforms and ESPs often necessitates SPF flattening, as each integration adds to the DNS lookup count.
Email marketer from AuthSMTP explains that SPF flattening should be considered when you are using multiple email service providers, and your SPF record is complex, approaching the limit of 10 DNS lookups.
Email marketer from SendLayer indicates SPF flattening becomes crucial when you start encountering SPF "permerror" issues due to exceeding the maximum number of DNS lookups allowed, which can cause emails to be rejected.
Email marketer from Reddit mentions that in practice, if you use more than two or three external services (like SendGrid, Mailgun, etc.) in your SPF record, you'll likely need SPF flattening to avoid exceeding the lookup limit.
Email marketer from SpamExperts suggests considering SPF flattening when you want to ensure maximum compatibility with different email receivers and to prevent potential deliverability problems stemming from SPF limitations.
What the experts say2Expert opinions
Expert from Word to the Wise answers that SPF flattening is a useful tool when an organization has multiple sending sources and their SPF record approaches the 10 DNS lookup limit, which can cause deliverability issues.
Expert from Spam Resource explains that SPF flattening becomes necessary when the number of DNS lookups required by your SPF record exceeds the limit of 10, leading to SPF failures and potential deliverability problems.
What the documentation says4Technical articles
Documentation from EasyDMARC explains that SPF flattening becomes necessary when an SPF record exceeds the 10 DNS lookup limit. This limit, set to prevent denial-of-service attacks, can be problematic for organizations using multiple third-party email services.
Documentation from Google Workspace Admin advises that if your domain sends email from more than one source (e.g., in-house servers and third-party senders), you should evaluate your SPF record. If the lookups approach 10, consider SPF flattening.
Documentation from DMARC Analyzer explains that SPF flattening is used to reduce the number of DNS lookups in an SPF record, which is crucial for preventing SPF validation failures when the limit of 10 lookups is exceeded.
Documentation from RFC 7208 specifies that SPF implementations MUST limit the number of mechanisms and modifiers that cause DNS lookups to at most 10 per SPF check, which necessitates SPF flattening when this limit is reached.