What you’re seeing
- Bounces mention code 5.4.6, a routing loop, or that the hop count was exceeded.
- Mail to one user, one domain or one forwarding address fails while other mail works.
- The bounce message lists a long chain of server headers, with the same servers appearing repeatedly.
- The problem began after a migration, a new filtering service or a forwarding rule was set up.
Common causes
Every environment is different, but these are the causes our engineers find most often:
- A domain is set as authoritative in two places, so each system forwards mail for it to the other.
- A mailbox forwards to an address that forwards back, directly or through a chain of rules.
- During a hybrid or staged migration, a mail user object points back to the system that already sent it.
- MX records and connector settings disagree about which service is the final destination for a domain.
- A third-party filtering gateway and Microsoft 365 are each set to route mail through the other.
Why it matters
A routing loop means mail for the affected addresses cannot be delivered at all, and every attempt consumes server resources until it is stopped. If the loop involves a whole domain, customers trying to reach your staff get bounces and may conclude you are out of business or that their message was blocked. Loops often appear during migrations, exactly when the business is least able to absorb email disruption.
How AskTechGurus fixes it
Skip the trial and error. A certified engineer works on your actual system, finds the root cause, and fixes it properly.
Tell us what’s happening
Submit a ticket in about two minutes. Paste the error, describe what changed, and pick your tier. No charge to submit.
A certified engineer diagnoses it
A vetted, US-based systems engineer claims your ticket, usually within minutes during business hours, and investigates over a secure remote session you can watch and end at any time.
Fixed and verified with you
The engineer resolves the root cause and confirms with you that it’s working. You don’t just get a workaround, and you get a plain-English summary of what was wrong.
Pay only when it’s resolved
Fixed price from $99, invoiced only after you approve the fix. If it isn’t resolved, you don’t pay.
Frequently asked questions
Could this be affecting more people than we know?
Possibly. A loop can apply to a single address or an entire domain. Part of the diagnosis is determining exactly which recipients are caught in it.
Is our email system damaged?
No. A loop is a configuration conflict, not damage. Once the systems agree on where mail should end up, delivery goes back to normal.