Fix NDR error "550 5.7.133" in Exchange Online

Article
01/24/2024

It's frustrating when you get an error after sending an email message. This topic describes what you can do if you see error code 550 5.7.133 in a non-delivery report (also known as an NDR, bounce message, delivery status notification, or DSN). You'll see this automated notification when the recipient is a group that's configured to reject messages from external senders, that is, senders from outside the organization.


	I got this bounce message. How do I fix this issue?		I'm the group owner or email admin. How do I fix this issue?

I got this bounce message. How do I fix this issue?

Only the group owner or an email admin in the recipient's organization can fix this issue. Contact the group owner or email admin and refer them to this information so they can try to resolve the issue for you.

I'm the group owner or email admin. How do I fix this issue?

The two methods that will allow an external sender to send messages to the distribution group in your organization are described in the following sections.

To open the Exchange admin center (EAC), see Exchange admin center in Exchange Online.

Method 1: Allow all internal and external senders to send messages to this group

New Exchange admin center (EAC)

Go to Recipients > Groups.
Select a group from the list and click it. The group properties screen appears.
Click the Settings tab.
Under Delivery management, click Edit delivery management. The Delivery management screen appears.
Under Sender options, choose Allow messages from people inside and outside my organization.
Click Save changes.

Classic EAC

In the EAC, go to Recipients > Groups > select the group from the list, and then click Edit .
In the group properties dialog box that opens, go to Delivery management > select Senders inside and outside of my organization.
Click Save.

Method 2: Use the group's allowed senders list

Instead of allowing all external senders to send messages to this group, you can use the group's allowed senders list to selectively allow messages from all internal senders and the specified external senders.

Notes:

To add an external sender to a group's allowed senders list, you must first create a mail contact or a mail user to represent the external sender in your organization.
To add everyone in your organization to a group's allowed sender's list, you can create a distribution group or a dynamic distribution group that contains everyone in your organization. After you create this group, you can add it to the group's allowed senders list.
The group's allowed senders list is different from the organization's allowed senders list for anti-spam that you manage in the EAC at Protection > Spam filter.

To configure the group's allowed senders list, perform the following steps:

New EAC

Go to Recipients > Groups.
Select a group from the list and click it. The group properties screen appears.
Click the Settings tab.
Under Delivery management, click Edit delivery management. The Delivery management screen appears.
Under Sender options, choose Allow messages from people inside and outside my organization.
Under Specified senders, click inside the text box. The list of senders (internal and external) is displayed.
Choose the senders you want to add to the senders list, and click Save changes.

Classic EAC

Go to Recipients > Groups > select the group from the list, and then click Edit .
In the group properties dialog box that opens, go to Delivery management and configure the following settings:
- Select Senders inside and outside of my organization.
- Click Add . In the Select Allowed Senders dialog box, select and add the external senders and the "all internal users" group. When you're finished, click OK.
Click Save.