https://senderaudit.com/blog/en/tags/esp/Recent content in ESP on Sender Audit BlogHugoenThu, 05 Mar 2026 00:00:00 +0000https://senderaudit.com/blog/en/double-dkim-signature/Thu, 05 Mar 2026 00:00:00 +0000https://senderaudit.com/blog/en/double-dkim-signature/<p>You inspect the headers of an email sent through your ESP (Brevo, Mailchimp, SendGrid…) and notice <strong>two distinct DKIM signatures</strong>: one with your domain, one with the ESP&rsquo;s domain. Is this normal? Absolutely, and it&rsquo;s actually desirable.</p> <h2 id="what-it-looks-like-in-the-headers">What It Looks Like in the Headers</h2> <p>Here&rsquo;s a typical <code>Authentication-Results</code> example:</p> <pre tabindex="0"><code>Authentication-Results: mx.google.com; dkim=pass header.i=@yourdomain.com header.s=mail header.b=xjAWgYt1; dkim=pass header.i=@esp-domain.com header.s=mail header.b=zNRqfud1; spf=pass ... dmarc=pass (p=REJECT) header.from=yourdomain.com </code></pre><p>And two <code>DKIM-Signature:</code> blocks in the message: one with <code>d=yourdomain.com</code>, the other with <code>d=esp-domain.com</code>.</p>