Glossary
Mail loop
Messages passing back and forth between systems without end, usually from two auto-replies answering each other or a bad forwarding rule.
ValidReach Team · Updated 2026-10-26
In practice
Servers stop loops by counting the Received headers and rejecting a message that has passed too many hops. Mark automatic replies as automatic so others do not answer them.
Verification and sending
Not related to verification; it is a routing fault.