Hello again,
I appologise that I was not clear in my last post.
These letter's I recieve are snail mail, not email.
Sorry for the confusion.
However I don't think that it would be spam if you recieved a email from them first, they are giving you permision to contact them. You would just have to take the approcch that you want more information on their program, then you ask them if they would be interested in learning about another opportunity. If they say yes, that is how you would get there permission to send them an invitation. It seems a little time consuming but it is not spam they are giving you permission.