Welcome to the forums,
In the below COSname is 'default' unless you've specified others. Anything with zimbraPref is possible as an individual user setting that can override class of service when set explicitly on an account, if not set it just inherits the parent COS. These are also in the admin console GUI > COS/account > features & preferences tabs.
su - zimbra
zmprov mcf zimbraXMPPEnabled TRUE
zmprov mc COSname zimbraFeatureIMEnabled TRUE
zmprov mc COSname zimbraPrefIMAutoLogin TRUE
zmprov mc COSname zimbraPrefIMNotifyPresence TRUE
zmprov mc COSname zimbraPrefIMNotifyStatus TRUE
zmprov mc COSname zimbraPrefIMReportIdle TRUE
Notifications:
zmprov mc COSname zimbraPrefIMFlashIcon TRUE
zmprov mc COSname zimbraPrefIMFlashTitle TRUE
zmprov mc COSname zimbraPrefIMSoundsEnabled TRUE
(NE also has YIM interop included in addition to local ZCS-Wildfire IM.)
Some external XMPP/Jabber clients:
Pidgin and Zimbra - Zimbra :: Wiki Spark and Zimbra - Zimbra :: Wiki Adium and Zimbra - Zimbra :: Wiki