This is the first time I had recieved this mail...
I don`t know if it`s a virus or not.
However, if you don`t know who it`s from, you should delete it.
I get them all the time in an account I specifically set up to collect spam.
I've never bothred finding out what they are, but my best guess is that such emails have been removed from the system due to some kind of objectionable content - be it a virus or whatever.