Link to open microsoft communicator

Hello,

I am trying to make a hyperlink that opens a communicator window with a certain user. I have tried sip:user@domain.com and im:<sip:user@domain.com> but nothing works.

If i copy and paste sip:user@domain.com into the search bar for IE it will work perfectly! but I need a hyperlink to do this.

I have tried <a href> and that will open outlook?

Anyone have any suggestions or thoughts.

Thanks