Exchange Mail Flow Rule

Copper Contributor

I have created a mail flow rule blocking a group from sending emails outside of the organization.  This is working fine.

I am attempting to create a rule for the same group so they can not receive emails from outside the organization.  When activated, it is also blocking organization emails.

I have selected 'The Sender is Located' 'Outside Organization'.  'The recipient is a member of' 'BLAH Group',  and have selected 'Reject...'.

Not sure if there is an issue, or I am missing something with the rule creation.


Thanks in advance for the assist.


5 Replies

Hard to tell without seeing the rules, but you can run a message trace to confirm the message is being blocked by some rule. You don't need transport rules for that btw, just toggle the -RequireSenderAuthenticationEnabled flag.

Thanks for the reply.


Not to familiar with the Admin side.  Where exactly would that flag be located?


Regarding the blocking, I know it is the rule causing the issue.  I have a mailbox for the sender and I am getting a un-deliverable when testing.



Sorry for the extra message. 


What I just thought of regarding authentication, all users in that group are not authenticated.  They are using the web to log into emails.  No AD account being used..


I just came across 'Delivery Restrictions' that is available with in the users configuration.  That seems to be a viable solution.  Place ALL into that group an they should only receive from them?




At default only people in the organization can send a mail to this group . You can double check by going to 

Exchange->Recipients->groups->double click on the group->Delivery management and see options 

Check image below 


Yes, the delivery restrictions is what I meant, and the flag I mentioned distinguishes between internal and external users as explained by @samuela2395