Expanding Mail-Enabled Groups

When mail is sent to a mail-enabled group, the group is first expanded, and then mail is sent to each of the recipients in the group. Unless an expansion server (a server that is responsible for expanding distribution groups) is specified, the group will be expanded on the first Exchange server that handles the message.

Expansion of large groups can tax system resources on an Exchange server. For large distribution groups, you may want to designate a dedicated expansion server to reduce the workload of the other production servers. Mail sent to large distribution groups will not slow the Exchange servers that your users use to access their mailboxes.

There is a drawback to setting a specific server as the expansion server for a group: If that server is unavailable, no member of the distribution group receives the message. However, if you leave the default setting, Any Server in the Organization, most of the users receive their messages if one server fails. Also, if all members of a distribution group are on well-connected servers, setting a specific expansion server may be unnecessary.

For information about setting specific expansion servers, see "Managing Recipient Settings."