Yes, I really did receive xanthophytes on mail art.
And the mail art was XL, as it didn't fit through the mail slot (or on the scanner). And it came with eXtra intelligent mail barcode labels - count them, they add up to half of X.
I recommend enlarging the picture of the whole envelope to appreciate the galaXy stripygoose sent me.
And inside was a new Starling Wars piece of mail art
And standing up: