I think it is odd to include the http//
No one does that or uses that looking up a website.
Also, it is written to look like someone not very educated- textspeak- ur, 2, but it reads oddly as if it is trying to create that impression.
All of the things about the name, address, letter, envelope strike me as someone trying to look the opposite of who they are so that you won't suspect them.
I say that because a number of years ago I had 2 anonymous letters which were sent to me at work about my then just ex-partner, telling me he was screwing around and did not 'luv' me. They were bizarre- short, poor spelling, odd address with unusual errors in the content (dated language).
They turned out (I am pretty sure) to be from a woman at his job who must have had an absolute obsession with him. (They both worked at social services and I had met her a couple of times on nights out.) She was much older than us- about 18 years- and very loud with him, laughing lots at anything he said. We had joked about it at the time.
I discovered it was her because she had to send me some notes from a meeting about a year later and she made two of the same, very unusual errors in my job title and work address. I am sure it was her.