Glossary · Email

Email Forwarding

Email forwarding automatically redirects incoming mail from one address to another, often at a different provider, which can break SPF and DMARC checks.

Updated October 6, 2026

Email forwarding is the automatic redelivery of messages received at one address to another address. It is commonly set up for custom-domain mail, closed accounts and role addresses.

Why it matters

Forwarding is convenient, but it interacts badly with authentication. A forwarded message is re-sent from the forwarder's server, so the original sender's SPF record does not authorise that IP and SPF fails. DKIM survives if the message is unchanged, which is why signatures matter, and ARC lets trusted forwarders record the earlier results. Some forwarders rewrite the envelope sender (SRS) so SPF can pass against their own domain, but that does not align with the original From domain.

Example

sales@example.com -> forward -> jane@gmail-style-provider.test

A message from bank.test, which has a strict DMARC policy, arrives via the forwarder. SPF fails because of the forwarder's IP, but the original DKIM signature still passes and aligns, so DMARC passes. If the forwarder had added a footer, the DKIM signature would break and the mail could be rejected.

Common mistakes

  • Forwarding mail to a provider that treats forwarded spam as originating from you.
  • Assuming SPF will pass after forwarding.
  • Setting up forwarding loops between two mailboxes.

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