# 5.7.124 Bounce: Sender Not in Allowed Senders List

URL: https://email-validation.org/bounce-codes/5-7-124/
Updated: 2026-11-06

> Documentation index: https://email-validation.org/llms.txt

**At a glance**

- **Type:** permanent failure (class 5, RFC 3463 §2). The sending server does not retry; sending the same message again fails the same way until the cause is fixed.
- **Basic code:** varies; the enhanced code is the part that identifies the problem.
- **Enhanced code 5.7.124:** not in the IANA registry; the group is security or policy status (RFC 3463 §3.8).
- **Who uses it:** Microsoft (Exchange Online): sender not in the allowed-senders list of a group.

A 5.7.124 bounce from Microsoft 365 means you wrote to a group (a distribution list) that accepts mail only from a list of approved senders, and you are not on that list. Your message did not reach any member.

## What it means

This is Microsoft's code, not one from the IANA registry. Microsoft's [Exchange Online NDR reference](https://learn.microsoft.com/en-us/troubleshoot/exchange/email-delivery/ndr/non-delivery-reports-in-exchange-online) describes it as a sender who is not in the group's allowed senders list.

In Exchange Online, a group owner or admin can limit who may send to a group to specific people or groups. Anyone else gets this bounce. It is a deliberate setting, often used on large internal lists such as an all-staff address, so that only a few people can mail everyone.

## Common causes

- You are outside the organization, and the group accepts only named senders.
- You are inside the organization, but not one of the approved senders.
- You were approved, but under a different address than the one you sent from (an alias, or a personal account).
- You are sending from an automated system whose address was never added.

## How to fix it

If you are the sender:
1. Check that you wrote to the right group. A personal address or a different list may be what you need.
2. Send from the address the group knows, if you have more than one.
3. Ask a group owner, or someone who can already send to the group, to pass your message on or to request access for you.

If you own or administer the group:
1. Open the group's delivery management settings in the Exchange admin center or the Microsoft 365 admin center.
2. Add the sender, or a group the sender belongs to, to the allowed senders.
3. If the restriction is no longer wanted, change it to allow everyone in the organization, or everyone including outside senders.

Only the recipient's side can change this. Nothing in your own mail setup will make the message go through.

## A similar code

If the group, mailbox or public folder refuses all mail from outside the organization, rather than allowing a list of named senders, Microsoft returns [5.7.133](https://email-validation.org/bounce-codes/5-7-133/) and its sibling codes instead. Many other recipient-side refusals use [550 5.7.1](https://email-validation.org/bounce-codes/550-5-7-1/).

## What to do with the address

Keep it. The group exists; it just does not accept your mail.

## Related codes

- [5.7.133](https://email-validation.org/bounce-codes/5-7-133/): The group or mailbox takes no mail from outside (Microsoft 365)
- [550 5.7.1](https://email-validation.org/bounce-codes/550-5-7-1/): Delivery not authorized: refused for policy reasons

See [every bounce code](https://email-validation.org/bounce-codes/) in the dictionary.

Many bounces from addresses that do not exist can be avoided: check an address with our [free email checker](https://email-validation.org/email-checker/), or [clean a whole list](https://email-validation.org/bulk-email-verification/) before you send.