What is an email redirect?
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An email redirect is when a mail server automatically sends an incoming message to a different address without changing who the original sender appears to be. The "From" line stays the same, the message just ends up somewhere else.
This is different from forwarding. When you forward an email, you're the sender of the new message (it shows "Forwarded by you"). With a redirect, the original sender's address stays intact, which sounds convenient but creates authentication headaches.
Here's what happens: the original sender authenticated their message with SPF, DKIM, and DMARC for delivery to address A. The message arrives at address A's server, which then redirects it to address B. But address B's server sees a message claiming to come from the original sender, arriving from address A's server. The authentication doesn't match up anymore. DMARC fails.
You'll see this break most often with mailing lists and university email systems. A message gets sent to listserv@university.edu, the list redistributes it to 500 members, and suddenly half the copies land in spam because DMARC alignment failed. The receiving servers think someone's spoofing the original sender. This DMARC-breaking problem was so common that a new standard called ARC (Authenticated Received Chain) was created to fix it. ARC acts like a chain of custody receipt. Each server that handles the message adds its own signature saying "yes, this was authenticated when it arrived here, and here's proof." The final receiving server can check the ARC chain and see that the message was legitimate at the start, even if the redirect broke the original authentication.
Most major mailbox providers (Gmail, Yahoo, Outlook) now support ARC, but not all mail servers have implemented it yet. If you run a mailing list or an email forwarding service, enabling ARC on your mail server helps keep legitimate redirected mail out of spam. If you're a sender whose messages are getting redistributed through mailing lists, there's not much you can do except hope the list operator has ARC configured.
If you're troubleshooting why messages sent through a mailing list are landing in spam, check your DMARC reports for alignment failures. If you see failures coming from known mailing list servers, that's the redirect problem. The fix is on the list operator's side, not yours.
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