Looks like a completely scam.
1. Entire copy paste of the
http://blender.io mixer website. Didn't even bother to change the logo.
2. The same deposit address always shows up when you try to "mix coins" (1BA6SjUffu2UM7ZNpdofVQUrCc4Lrnf5et), and you don't even have to input anything (not even the receiver's bitcoin address).
3. Nothing else works (i.e the letter of guarantee). I bet you just copied the html of the blender.io website and added your own address there.
C'mon man, you can do better than this.