Hi I am running Exchange 2010 SP1. I have some newly created universal distribution list that are not receiving emails from external users. I read in some post that the checkbox should be unticked for require authentication, however I have some DL which were created some time ago and the box is checked and those groups are receiving emails without issues. Why the discrepancy. What is the best practice. Thanks

By default, when you create a distribution list, When you use the distribution list inside your organization, it works fine because the users are authenticated but the outside users aren't To work around Go to the distribution list's Properties. Click on the Mail Flow Settings tab. Double-click Message Delivery Restrictions. Uncheck the box "Require that all senders are authenticated." Thanks Mouzzam Hussain Visit to my Blog mouzzamh.wordpress.com

To find all static Distribution Groups in your environment that require authentication run: Get-DistributionGroup | ?{$_.RequireSenderAuthenticationEnabled -eq $true} If you'd like to modify them to all accept email from external senders then run: Get-DistributionGroup | ?{$_.RequireSenderAuthenticationEnabled -eq $true} | Set-DistributionGroup -RequireSenderAuthenticationEnabled $false} Jesper Bernle | Microsoft Community Contributor 2011 Awardee

Hi nubianbabe, Please double check the settings as partners said first. "What is the best practice." In previous versions of Exchange, by default, no recipients were configured to require all senders to be authenticated. In Exchange 2010, only new distribution groups and dynamic distribution groups are configured to require all senders to be authenticated. To prevent messages that originate outside of your Exchange organization from being delivered to distribution groups that are used for internal communications, you can configure these groups to require sender authentication. If the DG need to receive external mails, you should unticked the checkbox.Frank Wang TechNet Community Support

Hi nubianbabe, Any updates?Frank Wang TechNet Community Support