You can create groups of contacts to send instant messages to multiple users at the same time. By default, every user is part of the All Users group.
To create a contact group
Open the Messenger window.
On the Contacts tab, right-click All Users or a named group, and then click Create a new Group.
The Group Setup dialog box appears.
Set up the following options:
Group Name - Enter a name for the group.
Group Type - Select one of the following options:
Private - With this option selected, when someone replies to the sender of a message, the reply is sent only to the original sender. In effect, it is as if the original sender has sent the message to everyone in the group individually.
Global - With this option selected, when someone replies to the sender of a message, the reply is sent to every member of the group unless the original sender is not a member of the group; in which case, the reply is sent only to the original sender.
Note: When someone replies to the sender of a message, the status of the Reply to ALL checkbox indicates whether that reply is being sent to one person or to a group.
Users - Do the following as needed:
To add
a user to the group, select that user under Available
Users, and then click the Add
button 
.
To remove
a user from the group, select that user under Users
Selected, and then click the Remove
button 
.
Click OK.