SPF, DKIM, and DMARC together — why the missing DMARC record was blocking registration emails
Background Registration confirmation emails were not reliably reaching users on Gmail and Outlook outside Japan — sometimes landing in spam, sometimes not arriving at all. Investigation pointed to a single root cause: the wpmm.jp domain had SPF and DKIM configured, but no DMARC record . What each of the three does SPF (Sender Policy Framework) declares in DNS which IP addresses are authorized to…
Registration confirmation emails failed to reach recipients on Gmail and Outlook outside Japan due to missing DMARC records. SPF and DKIM were in place, but no DMARC record was present. SPF checks authorized IP addresses, DKIM adds a signature to message headers and body, and DMARC sets how to act when SPF and DKIM checks fail. Without DMARC, there was no single policy for alignment results.
To address the issue, a DMARC record was added to the wpmm.jp domain's DNS. The TXT record specified to collect data without rejecting mail, with instructions sent to info@wpmm.jp for aggregate reports. This allowed tracking of mail passing or failing SPF/DKIM checks. The sender first tightened the code that sends emails, ensuring failure was detected and reported.
Headers like Reply-To, Date, and Message-ID were added to reduce spam scores. After adding the DMARC record, Google began sending aggregate reports, confirming legitimate mail from wpmm.jp passed DKIM checks while spoofed mail failed. This allowed the sender to monitor the situation rather than relying on user complaints.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
