No, it is an urban legend.
See the related question below.
David Gregory - historian - died in 1767.
1767
John David Gregory is 5' 11".
No , its a fake he was never found dead and did not die from not forwarding the message.
David Gregory was born on June 3, 1659.
David Gregory was born on June 3, 1659.
John David Gregory is 5' 11".
Ryan David Gregory is 6' 3".
David Gregory Kays was born in 1962.
David Gregory - historian - was born in 1696.
Nobody knows which David Gregory this is, but there is a journalist named David Gregor that is still living today.
No. It's just a hoax.