How to Stop Forwarded Emails From Creating an Endless Mail Loop

An endless mail loop is one of the most annoying email problems you can face. Two inboxes keep forwarding the same message back and forth, your mailbox fills up with hundreds of copies, and important mail gets buried. It usually starts with a simple forwarding rule that seemed harmless at the time.

The good news is that a mail loop is easy to stop once you know where to look. You do not need special tools. You just need to find the rules that are bouncing the message around and break the circle in the right place.

Quick Answer

To stop a forwarded email loop, pause or delete the forwarding rule on one of the accounts involved so the circle is broken. Then check both inboxes for auto-reply rules, filters, and server-side forwarding settings, because loops often involve two rules working together. Delete the duplicate messages, wait a few minutes for queues to clear, and test with a single new email before turning any forwarding back on.

What Is an Email Forwarding Loop?

A mail loop happens when a message is forwarded automatically from Account A to Account B, and then Account B automatically forwards it back to Account A. The process repeats over and over. Each trip can add another copy to both inboxes.

Sometimes three accounts are involved. For example, your work email forwards to your personal email, your personal email forwards to a team inbox, and the team inbox forwards back to your work email. The message travels in a circle with no natural end.

Modern mail servers try to detect loops and stop them after a set number of hops. That protection helps, but it is not perfect. If the subject or headers change slightly during forwarding, the server may treat each copy as a new message and let the loop continue.

Common signs you are in a loop

• You receive the same subject line dozens or hundreds of times.
• New copies arrive every few seconds or minutes.
• Your mailbox quota warning appears suddenly.
• Other people tell you they are getting repeated copies too.
• The sender address alternates between two of your own addresses.

Step 1: Stop the Damage First

Do not start by deleting messages. If the loop is still active, new copies will replace the ones you delete. Break the loop first, then clean up.

1. Open the settings for the first account you control.
2. Look for Forwarding, Rules, Filters, or Inbox Rules.
3. Temporarily disable every auto-forward rule. Do not delete them yet if you need to remember what they did.
4. Repeat the same check on the second account.
5. Wait five to ten minutes. Most mail queues will empty in that time.

If you do not control one of the accounts, contact its owner or IT admin right away and ask them to pause forwarding to your address. A short, clear message works best: explain that a loop is happening and name the two addresses involved.

Step 2: Find Every Place Forwarding Can Hide

Forwarding is not always in one obvious place. Many people fix the client rule but miss the server rule, so the loop starts again. Check all of these locations.

In your email app

Apps like Outlook, Thunderbird, and Apple Mail have their own local rules. A message filter that says “forward to” or “redirect to” can keep running even if server forwarding is off. Review each filter one by one and look at the action, not just the name of the rule.

On the webmail or server settings

Log in to webmail for Gmail, Outlook.com, Yahoo, or your company mail and check Settings, then Forwarding. Also look for auto-reply or vacation responder settings. An auto-reply that includes the original message can restart a loop when it meets another auto-reply.

For more detail on how forwarding works in Microsoft accounts, see the official guide to automatic forwarding in Outlook.com from Microsoft Support. Google users can review the instructions for automatically forwarding Gmail messages to another account to see where that setting lives.

At the domain or admin level

If you run a business domain, forwarding may also be set in your admin console or in your mail host control panel. Aliases, distribution lists, and catch-all addresses are frequent hidden causes. A distribution list that includes an address that forwards back to the list is a classic loop.

Step 3: Fix the Rule Instead of Just Deleting Everything

Once the loop has stopped, decide what you actually wanted forwarding to do. Most people only need one-way forwarding. If both directions are on, that is usually the mistake.

1. Keep forwarding in one direction only.
2. Remove the return forwarding completely.
3. Add an exception so messages that came from the destination address are never forwarded back. Many systems let you add a condition like “except if sender is” and then enter the other address.
4. Use “keep a copy” carefully. It is useful for backup, but it can double the mess during a loop.
5. Save the corrected rule and send one test message. Watch both inboxes for five minutes.

If you use filters to organise mail rather than move it between accounts, you may also benefit from reading a clear explainer on how to create email filters to organise your inbox automatically, which covers safer filter conditions that do not trigger loops.

Step 4: Clean Up the Duplicate Messages Safely

After you are sure no new copies are arriving, it is safe to clean up.

1. Sort your inbox by subject or by sender to group the loop copies together.
2. Select a small batch first, for example 50 messages, and delete them.
3. Check that you have not selected a unique message with a similar subject.
4. Empty the Deleted Items or Trash folder if your mailbox is near its limit.
5. Repeat in the other mailbox that took part in the loop.

If other people were copied into the loop, send one short apology and explanation. Do not reply-all to a loop message itself, because that can create a fresh wave of replies.

How to Prevent Loops in the Future

A few simple habits prevent almost all forwarding loops.

• Draw the path on paper: Before you save a new rule, write down where the message starts and where it ends. If the path can return to the start, do not save it.
• One owner, one rule: Let one person manage forwarding for shared inboxes. Two admins creating rules independently is a common cause.
• Test with one message: Never turn on forwarding and walk away. Send a test, wait, and confirm you got exactly one copy.
• Review rules monthly: Old rules for projects that ended months ago are often forgotten and later combine with new rules to form a loop.
• Be careful with auto-replies: Set auto-replies to respond only once per sender where the option exists, and never combine an auto-reply with auto-forwarding on the same account without testing.

Common Mistakes to Avoid

• Deleting messages while the loop is still running: This wastes time and can make you miss the moment the loop actually stops.
• Fixing only one account: A loop needs at least two points. If you only check one inbox, the other half remains.
• Creating a new rule to “fix” the old rule: Extra rules add more paths for mail to travel. Edit or remove, do not stack rules.
• Using forward instead of redirect without thinking: Forwarding changes headers and can hide the original loop path, making diagnosis harder.
• Ignoring mailing lists: Adding a forwarding address to a list that already includes the source address is a loop waiting to happen.

Conclusion

An endless mail loop looks chaotic, but the cause is almost always simple: two automatic actions pointing at each other. Pause forwarding on one side, check every place a rule can hide, and clean up only after the flow of new copies stops. Then rebuild forwarding in one direction only, with an exception for the destination address, and test it with a single message. With a monthly review of your rules, you can make sure the same loop never returns and your inbox stays calm and usable.

Frequently Asked Questions

Why did my mail loop start suddenly when I changed nothing?

Someone else may have changed a rule on the other account, or a new rule you added combined with an old forgotten rule. Loops often need two changes at different times before the circle is complete, so the second change looks like the sudden cause.

Will a mail loop stop on its own?

Sometimes a server will stop it after a maximum hop count, but do not rely on that. Some loops run for hours and fill mailboxes completely. It is always faster and safer to disable one forwarding rule yourself.

Can a mail loop affect people outside my accounts?

Yes. If a mailing list, group address, or copied recipient is part of the path, they can receive many duplicates too. That is why stopping the rule quickly matters more than cleaning your own inbox first.

What is the difference between forwarding and redirecting?

Forwarding sends a new message from your address and often adds “FW:” to the subject. Redirecting resends the message while keeping the original sender visible. Both can cause loops if they point back to each other, so both need the same careful check.

How do I know the loop has fully stopped?

Wait at least ten minutes after disabling the rule and confirm no new copies with the same subject have arrived in either inbox. Then send one fresh test email and make sure you receive exactly one copy in the expected place.