Renamed 'email' variables to 'sender' to be in line with 'recipient'.
Renamed 'valid' variables to 'validSender' to be in line with 'validRecipient'.
Added print print statements relevant so far for easier reading/debugging.
Fixed a bug that allowed more instances of '@' to be entered for email adresses.
Added DATA recognition functionality. Added mail body input functionality.
Added email send print messages. Made variables 'sender' and 'recipient' global in order to use them.