Change from header in email, fixes #765
Remove unused "User" member of Message Struct and fix bounce address

The User member of a message is not needed anymore.

The from that is send to the server, should always be the "system" from. This is also called the Bounce address http://en.wikipedia.org/wiki/Bounce_address
Parse the from string to extract the email address
Merge pull request #766 from phsmit/correct_from

Correct usage of FROM in email creation