Notifications Can't Be Send :(

I get the following Email in my Inbox:-

A message that you sent contained no recipient addresses, and therefore no
delivery could be attempted.
------ This is a copy of your message, including all the headers. ------
ETC.
Hey <uname>!

Someone is now following your updates on FriendNation.

You can see his/her profile here: http://www.foo.bar/
--------------------------------------------------------------------------------------------------

Can You Tell Me Why Cant it be sent?