This is an issue one of my team mates Kevin shared with me about the new Aggregate Presence behavior in LCS vs. Exchange IM. For those customers who have used Exchange IM with WM 4.6, 4.7, 5.0 you may have noticed that when you sign in to multiple machines any text IM will be delivered to all end points. Kind of a broadcast approach.

When moving to LCS and using WM5 you may have had someone report that you never replied to their message. Below is a customer reported problem about this.

Reported Problem:
Customer using Windows Messenger from Home, leaves for work but does not recieve any instant messages. Upon returning home the IM client still signed in to had the messages.

Actual Problem:
In Exchange messaging, if a user was logged into two places, a message sent to him would go to both places.In LCS, it only goes to one.

Cause:
Presence and Aggregate Presence
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/rtcsrv/rtc/registrarendpoint.asp

Resolution:
To prevent this, on the machine at home lock the machine or sign-out of IM when finished using it to prevent the buildup of aggregate presence.

Cheers!
Toml LCS Kid