You can use the Enhanced-List Application (ELA) to create distribution lists for delivering messages to a large number of recipients.
Before you implement ELA, collect the following information:
An available Class of Service (CoS) number. (The default for ELA is 8.) ELA uses this CoS number for list mailboxes and the shadow mailbox.
A range of extensions to use for list mailboxes. You do not need this information to set up ELA but you need this information to provide extensions for the list mailboxes when you begin creating lists.