I'm trying to build a rule to reject a message with explanation when a given Distribution List is used in fields "To" or "CC". The goal is to force users to use "BCC" with this DL.
So far I found the header "X-MS-Exchange-Organization-BCC" could eventually help but I'm not sure how to use it.
Help appreciated :)
Hi @Djavan ROA,
try to use a transport rule with condition
"When the recipient is a member of 'yourgroup'"
"The To or CC box contains a member of 'yourgroup'"