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Allowing External Messages to Exchange Distribution List

tecpub asked
Hey Everyone -

Im trying to create a distribution list in Exchange 2010 in SBS 2011. Im using existing user accounts/mailboxes in AD, but need to accept emails from the outside. When I create the list, I check that in Mail Flow that "Authenticated Users" are not required. However, I'm getting a user not found error when sending email to the groups.

Note that I did create the group in Exchange 2010, not Active Directory. Not sure if that helps.
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Hendrik WieseInformation Security Manager


As long as "Require that all senders are authenticated" is unchecked external mail should come in just fine. So the next thing to check would be the address book sync. Try to update your address book by doing the following and let me know if it helps:

Please refer to my article to achieve this: Manually Update Global Address List (GAL) on Exchange 2010
Hendrik WieseInformation Security Manager

Don't know if you have an Edge server as well. If you do, run the following command from your CAS server:

Start-EdgeSynchronization -ForceFullSync

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systechSenior Technical Lead

Note the terminology differences between Active Directory and Exchange 2010. In Active Directory, a distribution group refers to any group that doesn't have a security context, whether it's mail-enabled or not. In Exchange 2010, all mail-enabled groups are referred to as distribution groups, whether they have a security context or not.

Please have a look at this MS article http://technet.microsoft.com/en-us/library/bb125178.aspx

Hope this helps!

Do you get mails on DL sent from internal users?
If you want to accept external email on Distribution email, the please follow below steps.

By default, Exchange only allows authenticated users to email distribution lists. To change this:

1. Open the Exchange 2007 Management Console
2. Expand Recipient Configuration, then Distribution Group
3. Open Properties of the group in question
4. Choose the Mail Flow Settings tab
5. Select "Message Delivery Restrictions" and hit Properties
6. Uncheck the "require that all senders are authenticated"
You can also restrict/allow senders more granularly if you like.

AND if you want to Add external email addresses to a distribution list, the follow blow steps

You need to create the external email addresses as Contacts in Active Directory. To do this, you'll need to leave the SBS wizards and use Active Directory Users and Computers.

1. Open ADUC from Administrative Tools
2. Navigate to Domain, right click and choose New -> Organizational Unit to create a new OU, and call it Contacts
3. Right Click on the new OU and select New -> Contact
4. Fill in the details for the contact, selecting an SMTP address - the SMTP address will be their external email address.
5. Now, you can add them to your distribution group(s)

Note: when you're adding them to the Distribution Group, you may need to explicitly include contact objects in the AD dialog box in the field "Select this object type".

Thank You.


I have followed your instructions but have not been able to send email to external email addresses inside a distribution list. Any ideas?