NDR 550 5.7.193 when external users send email to a Microsoft 365 group

Summary

External senders receive NDR 550 5.7.193 when they send an email message to a Microsoft 365 group that doesn't allow messages from external senders or when the sender isn't a member of the group. This article describes how group owners and administrators can resolve the issue by either adding the external sender as a guest member of the group or configuring the group to accept email from external senders by using Outlook, the Exchange admin center, or Exchange Online PowerShell.

Symptoms

An external sender receives the following nondelivery report (NDR) when they send an email message to a group in Microsoft 365 Groups:

The group <group name> isn't set up to receive messages from <sender name>.
More Info for Email Admins
Status code: 550 5.7.193
550 5.7.193 UnifiedGroupAgent; Delivery failed because the sender isn't a group member
or external senders aren't permitted to send to this group.

Cause

The Microsoft 365 group isn't configured to accept email messages from external senders or the sender isn't a member of the group.

Resolution

To configure a group in Microsoft 365 Groups to accept email messages from external senders, use either of the following methods. The method that you choose depends on whether you're an administrator or the group owner.

Method for group owner

Method 1: Add the external sender as a member of the group as a guest user

To allow a specific external sender to send email to the Microsoft 365 group, follow these steps:

1. Open the Microsoft Outlook Groups hub.

2. Select the group and then select Edit from the menu bar to open the Edit group dialog box.

3. Select the Members tab and then select Add members.

1. Manually type the email address of the external sender and select Add. This action adds the external sender as a guest member of the group. Select Close.

1. After you add the external sender, they appear as a member of the group under the Members tab.

1. Wait for the change to take effect. After that, the group accepts emails from this external sender.

Method 2: Enable people outside the organization to email the group

To allow all external senders to send email to the Microsoft 365 group, follow these steps:

1. Open the Microsoft Outlook Groups hub.

2. Select the group and then select Edit from the menu bar to open the Edit group dialog box.

3. In the Edit group dialog box, select Let people outside the organization email the groups.

**.

1. Select Save.

Method for administrator

Method 1: Add the external sender as a member of the group as a guest user

1. If the external sender isn't already a guest user, go to https://admin.cloud.microsoft/?#/GuestUsers and add the external sender as guest user. Follow the steps in Invite an external guest user.

2. Once you add the guest user, open Exchange admin center and go to Recipients > Groups. Select the relevant group to open the group details pane.

3. Go to the Members tab and click on View all and manage members.

4. Select Add members, select the external guest user, and then select Add. After you add the guest user, close the group page.

5. Wait for the change to take effect. After that, emails from this external sender are allowed to the group.

Method 2: Allow all external senders to email the group

1. Open Exchange admin center and go to Recipients > Groups. Select the group you want to manage to open the group details pane.

2. In the details pane, select Settings.

3. On the Settings tab, select Allow external senders to email this group.

4. Select Save.

PowerShell

1. Connect to Exchange Online PowerShell by running the following command:

   Connect-ExchangeOnline
   

2. Configure the group to receive mail from unauthenticated (external) senders by running the following command:

   Set-UnifiedGroup -Identity <group name or SMTP address> -RequireSenderAuthenticationEnabled $False