This is a fairly good question, all things considered. Truthfully Sherlock woke up at 3AM disoriented and unnerved and had the urge to talk to someone, anyone, but he hasn't got a flatmate and Chatroulette and Omegle are unfortunately slightly beyond Taxonian innovation at this precise moment. Sherlock's addressing his letter to the aliens. Sherlock's addressing his letter to the universe. Sherlock's unhappy about something, and pointless as it might be, he feels a little better now that messages are arriving in his inbox and someone has heard about it.
[text]
Nevertheless:
"To: [ALL]" -SH