Mail questions??

I have a couple quick questions about mail.

You create and alt or you just have a friend who is playing.

You decide to mail them gear, you figure if you can auction it or store it, you should be able to attach it and mail it.

So common gear meets this criteria, you can not list it for sale on AH but can mail it to another, Heroic gear meets this criteria, even if the receiver can not wear it due to lvl limitations, but Elite gear can not be mailed.

Is this an intentional thing or another glitch??

I mean I can send Heroic gear and seal stone but not Elite??

Anyone got any insight??