If invitation leter is a must, what about a invitation email? Has to be a paper letter?
I asked, invitation email is not useful. What I did was: prepare a letter in word, send it to my relative, they printed out, signed, scanned and email me, then I printed out.
When I presented this letter to visa office, she didnot bother to look at it, just put it in the bottom of the pile of papers, check my application forms very carefully.
But, if you donot have this letter, she may refuse you.
So, do as what I did, or if your relative is senior and has no scaner and computer, you just sign, scan,, and print out it, but make sure to let your relative know this in case ...
hope this help u.