SOLVED: Can't get URL 'shortcut' to work

I would like to have a link that opens the 'new mail' with a receipient.
I've used the URL like this:
mysite.com/index.php?option=com_uddeim&task=new&recip=Firstname%20Lastname
I've also tried
mysite.com/index.php?option=com_uddeim&task=new&recip=username
It opens the 'new message' window, but it doesn't fill in the user?

I even tried adding &nouserlist=3 and that is correctly interpreted, but the name is not filled in.

I also tried sending a message, in case the name was there, but hidden, but that told me that I needed to give a receipient.

Ahh, it is the UserID that is supposed to go there. Then it works, sorry didn't understand that at first.