The shadow mailbox is a special mailbox, analogous to a postmaster mailbox, that ELA uses to distribute messages. The use of a shadow mailbox prevents replies to ELA-delivered messages from being sent back to the entire enhanced list. However, you can administer enhanced-lists so that recipients can reply to the person who originally sent the message. The shadow mailbox must already exist in the system before you configure ELA.
You set up one shadow mailbox that serves all enhanced lists on the system.
To create the shadow mailbox: