Hi everyone,
I have distributive group on my Exchange 2013 server some.name@myorganisation.com and it is used for communication between members of that group. There are 15 members of that group. Now we need to include external member (external.member@partner.com) to that group.
I allowed mails to be sent to my group from outside organization and set transport rule to reject mail sent from outside organization except mail sent fromexternal.member@partner.com. It all works fine but I have some issues. When mail is rejected because it is not permitted sender I get NDR with reason why email is rejected (Sender is not permitted) and below list of all emails members of that group to which email is not delivered. I find that pretty much excessive as it reveals all members of my group. Also all of members get undelivered report which is not needed at all and is confusing for all users. It is pretty messy to look at those messages and is also somewhat security issue since spammer can get confirmation of existence of each emails in that group which makes them easy targets for future spam.
My question is if is there any way for these messages to be rejected silently without any NDR and undelivered report to each member of that group?