To customize the default e-mail message used when sharing data files over e-mail, follow these instructions. 

Step 1:

If you are using Windows XP, go to :
C:\Documents and Settings\[user-name]\Application Data\CoffeeCup Software\LockBox
 
If you are using Windows Vista or Windows 7/8, go to:
C:\Users\[user-name]\AppData\Roaming\CoffeeCup Software\LockBox
 
Note: Pressing Control+Shift+F12 will also take you to this folder location.
 

Step 2:

Double-click on the file email.txt
 

Step 3:

Make your changes and save the file.