SBS 2011 Distribution Group – error sending from “outside”

We wanted to send email from a promotion to several people in the sales department. ┬áTo do this we add a distribution group….

This is the error when you send in…

This is the mail system at host <>.
I’m sorry to have to inform you that your message could not be delivered to one or more recipients. It’s attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can delete your own text from the attached returned message.
The mail system
<address>: host 92.27.9.25[92.27.9.25] said: 550 5.1.1
User unknown (in reply to RCPT TO command)

Solution:

Don’t create the group in Active Directory Users and Computers.
Instead, create it in the Exchange Server Console.
Then, edit the properties and change the following…

Click on the Mail Flow Settings tab.
Double-click Message Delivery Restrictions.
Uncheck the box “Require that all senders are authenticated.”

Job done!

About mclark

20 years, Computer Engineer. Bsc Hons Computer Science, Durham Uni.
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