What the message looks like
554 5.4.6 Message exceeded 50 hops, this may indicate a mail loop554 5.4.14 Routing loop detected554 5.4.0 Error: too many hops
What it means
The email has passed between mail servers so many times that a server decided it must be going round in circles and stopped it. Each server adds a Received: header as it handles an email, and once there are too many, usually 50 or more, the email is rejected. The standard name for this status is "routing loop detected".
Common causes
- Two addresses forward to each other, such as an inbox that forwards to an alias, which forwards back to the same inbox.
- An auto-forward rule sends mail to an address that has its own forward back again.
- A domain's MX records point to a server that sends the mail back to where it came from.
- An auto-reply or vacation message replying to another auto-reply.
If you're the recipient
Check your forwarding rules, and those on any address you forward to. Look for a chain that leads back to the start, and remove one link from it.
If you're the sender
There's usually nothing wrong on your side. Let the recipient know their forwarding is set up in a loop.
If you use addy.io
addy.io rejects looping emails with 554 5.4.0 Error: too many hops. This usually means your recipient inbox, or a rule in it, forwards mail back to one of your aliases. Remove that forward, or change the alias's recipient so the chain ends at an inbox that doesn't forward.