Sender is outside organization

To approve email addresses from outside your organization and override the warnings in Outlook, you can add those email addresses to your allowed senders list. Here’s how you can do it:

1. Create a Mail Contact: If the sender is external, you first need to create a mail contact in your organization to represent that external sender. This can be done through the Exchange admin center.
2. Edit Group Settings: If you are managing a distribution group, you can go to Recipients > Groups, select the group, and then edit the delivery management settings to allow messages from external senders.
3. Allow All Senders: You can also choose to allow all internal and external senders to send messages to your group or mail user. This option can be found under the Delivery management settings in the group properties.
4. Mail Flow Rules: Consider using mail flow rules to bypass spam filtering for specific external senders. This can be configured in the Exchange admin center under mail flow settings.

By following these steps, you should be able to receive emails from external senders without warnings.

References:

• Fix NDR error "550 5.7.124" or "5.7.124" in Exchange Online
• Create sender allowlists for cloud mailboxes

Dear @Jay,

Thank you for reaching out to Microsoft Q&A forum.

I understand that you're having an issue receiving emails from senders outside your organization. The warnings you’re seeing, typically a banner such as “Sender is outside your organization” are known as External Sender Warnings. These are security features implemented by your organization’s IT department, usually through Microsoft Exchange Online Protection or Microsoft Defender for Office 365.

These warnings are generated at the server level before the email reaches your inbox, and they are not something that can be controlled or disabled from your individual Outlook client. The banner is inserted by your organization’s mail flow (transport) rules to help protect users from phishing or spoofing by clearly marking external messages.

Because these rules are centrally managed by your Exchange/Microsoft 365 Administrator, individual users are unable to permanently dismiss or bypass the warning regardless of how many times emails from a specific external sender are received.

To remove the warning for trusted external senders, your IT Administrator will need to update the mail flow rule that inserts the external banner. They can do this in one of the following ways:

1.Create an Exclusion List (Recommended):

• The Administrator needs to edit the existing Transport Rule that adds the external warning banner.
• They must add an exception to the rule: "Except if the sender's address is a member of this list (or matches this pattern)."
• They would then add the specific trusted external email addresses (e.g., trustedpartner@example.com) to this exclusion list.

2.Use a Group for Whitelisting:

• The Administrator can create a dedicated mail-enabled Security Group (e.g., "Trusted External Senders").
• They would add the external email addresses to this group as "Mail Contacts" or "Guest Users."
• The Transport Rule would then be configured with the exception: "Except if the sender is a member of the 'Trusted External Senders' group."

I hope this clarifies why the warning appears and provides workable solutions for your IT team. If you have any further questions or need additional assistance, please feel free to reach out. We’re always here to help. Have a wonderful day.

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".  

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.