How to open the DL for external user to send emails

Kumar, Pankaj 0 Reputation points
2026-10-14T13:24:16.3466667+00:00

How to open the DL for external user to send emails

Microsoft 365 and Office | Subscription, account, billing | For business | Other
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  1. AI answer

    2026-10-14T13:24:32.2066667+00:00

    For a distribution list or mailbox in Exchange Online, allow external senders by changing the message delivery restriction.

    For a mailbox:

    1. Open Exchange admin center.
    2. Go to Recipients > Mailboxes.
    3. Select the mailbox.
    4. Select Manage message delivery restriction.
    5. Under Accept messages from, clear Require senders to be authenticated.
    6. Select Save.

    If only specific external senders should be allowed instead of everyone:

    1. Create a mail contact or mail user for the external sender.
    2. Add that object to the mailbox's allowed senders list.

    For a Microsoft 365 Group:

    1. Open Exchange admin center.
    2. Go to Recipients > Groups.
    3. Select the group.
    4. Open Settings.
    5. Turn on Allow external senders to email this group.
    6. Select Save.

    PowerShell for a Microsoft 365 Group:

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

    If only one external sender should be allowed for a Microsoft 365 Group, add that sender as a guest member of the group instead of opening it to all external senders.

    AI-generated content may be incorrect. Read our transparency notes for more information.

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  2. Nam-D 4,410 Reputation points Microsoft External Staff Moderator
    2026-10-14T14:28:00.2+00:00

    Hello @Kumar, Pankaj

    To allow external users to send emails to your distribution list, you will need to update the delivery management settings in the Exchange Admin Center.

    Please follow the steps below:

    1. Extend Recipient > Groups
    2. Select your distribution list
    3. Go to Settings tab and select "Edit delivery management"

    User's image

    1. From Delivery management, select "Allow messages from people inside and outside my organization"

    User's image

    1. Click on Save button.

    If the setting have been already enabled this setting but external users are still unable to send emails to the distribution list, please share the complete error message, including any error code they receive when sending the email

    This information will help me better understand the issue and assist you further.

    Please feel free to share any updates with me. I look forward to hearing from you.

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