SMTP 554 5.4.14
Routing loop detected
554 5.4.14 means the message went round in a loop between mail servers until Microsoft stopped it. It is caused by a forwarding or connector misconfiguration, often on the recipient's side. The address itself may be fine, but nothing will deliver until the loop is fixed.
Should you remove the address?
Keep the address; fix the sending side
Keep the address but pause sending to it. The loop is a server setup problem, not proof the mailbox is gone.
Block. Retrying changes nothing until the cause on your side is fixed.
How it appears
Message exceeded 50 hops, this may show a mail loop.
What causes it
- Forwarding rules send mail back and forth between two systems.
- A connector or smart host routes the domain back to Microsoft 365.
- MX records point at a server that relays the mail straight back.
How to fix it
In order — try the first one first.
- If the recipient is at your own organisation, check forwarding rules, connectors and MX records for a loop.
- If it is an outside address, tell the recipient through another channel; only their admin can fix it.
- Pause sends to that domain until it delivers again.
Who sends it
Microsoft 365 and Exchange. Gmail reports a loop as 554 5.4.6 after too many hops.
Microsoft 365
Provider's description Routing loop detected
Microsoft says a configuration error caused an email loop, and Exchange stops it after 20 iterations by default.
Gmail
Reply text Message exceeded 50 hops, this may show a mail loop.
Gmail's equivalent, with 554 5.4.6.
Common questions
- What does SMTP 554 5.4.14 mean?
- 554 5.4.14 means the message went round in a loop between mail servers until Microsoft stopped it. It is caused by a forwarding or connector misconfiguration, often on the recipient's side. The address itself may be fine, but nothing will deliver until the loop is fixed.
- Should I retry a 554 5.4.14 error?
- No. 554 is a permanent failure, so the message will never be delivered no matter how many times you try. Remove the address — repeated sends to permanent failures are one of the main signals mailbox providers use to throttle a sender.
- How do I fix SMTP 554 5.4.14?
- If the recipient is at your own organisation, check forwarding rules, connectors and MX records for a loop.
- Is 554 5.4.14 a hard bounce or a soft bounce?
- 554 5.4.14 is a block rather than a classic hard or soft bounce. The rejection is about your sending (authentication, reputation, content or the recipient's policy), not about whether the address exists. Retrying changes nothing until the cause on your side is fixed.
- Should I remove the address after a 554 5.4.14 bounce?
- Keep the address but pause sending to it. The loop is a server setup problem, not proof the mailbox is gone.
- Will verifying my list prevent 554 5.4.14?
- No. A loop is a routing problem between servers; verification does not change it.
Clean the list before the next send.
A bounce report only tells you about the addresses you already mailed. The rest of the list has the same kinds of dead mailboxes in it, and each one becomes a hard bounce recorded against your domain the moment you send.
- A real SMTP mailbox check on every row, before anything is sent
- Dead and mistyped addresses split out, so they never reach your sending tool
- Catch-all, disposable and role addresses flagged alongside
One plan, cancel anytime, no contract. Sign in with Google and your first 100 email checks are free, no card. The free tools stay free either way.
Other 554 replies
Sources
- Source: Microsoft Learn: Email non-delivery reports and SMTP errors in Exchange Online
- Source: Google Workspace Admin Help: Gmail SMTP errors and codes
- Source: RFC 3463: Enhanced Mail System Status Codes
Provider wording is quoted only where the provider publishes it.
Last reviewed 2026-10-22