Kerio Connect mail server recently added Instant Messaging support. When I first heard that, I thought it was absolutely rediculous! If you want IM, open up the ports in your firewall and let it go.. why on earth do you need the mail server involved? I'm not generally a big fan of IM anyway, so I just dismissed this idea entirely.
Not so fast
I was wrong. Actually, there are some real benefits to passing IM through the mail server.
The first is that, by default, the only people who can use IM are those who are in your mail domain(s). You aren't opening up IM so that Bill can waste away the day chatting about sports with his friends. Moreover, if you don't want Bill to use this at all, you can assign a policy that prevents him from using IM. Or, you can make a default policy that prohibits IM to everyone and add an IM allowed policy for specific users.
If you only want this within your domain and aren't going to restrict anyone, there's nothing to do at the server: it's ready to work - it's in Services and is running by default.
As most IM clients now support such things as video, file sharing, screen sharing and group chat, you also have all that available - again, for the people you choose only.
Of course, IM is also a way to see if someone is available without bothering them with a phone call.
Although I'm a very small organization, I can see using this myself to get a quick message to my wife when I am out of the office. As long as I have Internet access, I can use IM to reach her and she can reach me - without having opened up IM access to the world at large!