I noticed the issue while configuring transport rule which would bounce undesirable mail to sender.
As the message is bounced, senders receives a reply (the sample below), which reveal all individual addresses of members of that distribution list. This creates a security breach, as spammers may use it to collect individual email addresses of users. Is there any way to hide the addresses in the return message, or to edit the template for that message?
Delivery has failed to these recipients or distribution lists:
<email1@domain>
Your message wasn't delivered because of security policies. Microsoft Exchange will not try to redeliver this message for you. Please provide the following diagnostic text to your system administrator.
<email2@domain>
Your message wasn't delivered because of security policies. Microsoft Exchange will not try to redeliver this message for you. Please provide the following diagnostic text to your system administrator.