I followed the link below but it doesn't allow me to signup.
I'm certainly over 13 perhaps your beta is good for US only?
To my surprise I got a reply about 3 weeks later, from a named person not a machine
We are aware of several issues our customers are having when trying to join the beta. We are deeply sorry for any inconvenience this may have caused you. We are currently sorting things out. Your patience is great appreciated during this time. I will add you to the list of customers waiting to be ported over to the Windows Live Mail Beta. Worst case scenario we'll send out new invitations. If you have any questions in the future please feel free to email me at the address listed below.
In my reply I did promise that I'll use their beta for work, the best way to test things out, hoping that they'll move me further up in the queue. Microsoft's latest reply was
I hope to have things sorted real soon.
Short and sweet this one, surely from a human being.