How is an email counted when sent to a Distribution List? (4298953)

How is an email counted when sent to a Distribution List?

There are a few answers depending on what perspective the question is being asked. In most cases, this perspective is from the Mailbox, if a user sends an email to a DL, then the DL is counted as one recipient, regardless on the number of members that make up that DL. In addition, the message will also be sent to each member of the DL.

For Mailbox Activity reports, MessageStats provides a count of Internal and External counts which take into account the logical recipient. A logical recipient is a recipient who is directly referenced in a message. So if a DL is a direct recipient, it will be counted as a single recipient, regardless of the number of members that make it up. DL expansion will then be performed by Exchange and the message sent to each member of the DL resulting in MessageStats counting a message recieved by each DL member mailbox. For example:

A message is sent to a DL with 3 members. MessageStats will count 1 message recieved for the DL and one message recieved for each of the 3 members.