When is SPF flattening needed and how to validate SPF records?
Summary
What email marketers say7Marketer opinions
Email marketer from MXToolbox shares that SPF flattening should be used as a last resort. Where possible investigate a subdomain solution so messages from third party providers use different SPF records.
Email marketer from StackExchange answers that not setting up SPF correctly or exceeding the limits can lead to emails being marked as spam, potentially damaging sender reputation and affecting email deliverability. SPF flattens helps minimize the risks.
Email marketer from EasyDMARC explains that SPF validation can be done by using online SPF record checker tools to ensure correct syntax and that the lookup limit is not exceeded. Also, DMARC reports can help track SPF validation results.
Email marketer from Reddit shares that you can validate SPF records using `dig` command-line tool or online SPF checking services to verify that the SPF record is correctly set up and that the number of DNS lookups does not exceed the limit.
Email marketer from Mailhardener states that SPF flattening might be needed when your SPF record contains too many nested includes, which causes the number of DNS lookups to exceed the allowed limit of 10.
Marketer from Email Geeks recommends using DMARC reports to validate the Return Path of each domain being used.
Email marketer from dmarcian explains that SPF flattening is useful when you have many third-party senders but it can create management headaches as IP addresses can change, so it is best practice to simplify your SPF record first and consider a subdomain strategy.
What the experts say3Expert opinions
Expert from Email Geeks explains that if SPF is configured correctly, SPF flattening might not be necessary, and better subdomain management might be a better solution.
Expert from Email Geeks explains that different services typically use different return paths, and SPF records are only needed for the return path, not any other domain. He advises to check the return path of mail sent by each service and only include services using the apex domain in the SPF record.
Expert from Word to the Wise recommends using tools like `dig` or `nslookup` to validate SPF records. These tools allow you to check the SPF record's syntax and ensure it doesn't exceed the 10 DNS lookup limit. You can also use online SPF record checkers.
What the documentation says4Technical articles
Documentation from Google Workspace Admin Help explains that SPF records have a limit of 10 DNS lookups. If this limit is exceeded, SPF flattening may be needed or the SPF record will fail, causing deliverability issues.
Documentation from Microsoft indicates that SPF flattening becomes essential to maintain email deliverability when a domain utilizes numerous third-party services for sending emails, leading to exceeding the DNS lookup limit within the SPF record.
Documentation from Valimail explains that SPF flattening should be avoided if possible by using a DMARC policy of reject so messages from invalid sources will be blocked completely.
Documentation from RFC 7208 specifies how to validate SPF records by checking the 'Received-SPF' header in the email. It confirms if the sending server is authorized to send emails on behalf of the domain specified in the 'Return-Path' address.