Windows Live Messenger with a non hotmail / msn email address

I am having problems with my windows live messenger. I don't use a msn or hotmail address, this itself does not pose a problem with other Internet contacts using Windows Live Messenger. The problem occurs adding contacts I have who connect using LCS, the corporate edition. They are able to add external cotacts if they have hotmail/msn email addresses. However they were unable to get me working or visa-versa. I add the contact successfully, but they never appear online, even though they are online! I have seen the post on the Microsoft site saying they need to add me as joeblogs(gmail.com)@msn.com. The funny thing is that this worked once and then the organisation upgraded their clients and we were back to square one. Any ideas??