First, make sure the audio you want is in solo mode on that track. (If its the only track then don’t worry about that.)
Second go to the file menu and select the bounce to disk option.
In the dialog box that pops up, make sure you select AIFF mono (summed) and whatever sample rate you desire-most likely 48k- and click ok
Then it will ask you where to save the file and what to name it. I recommend the desktop in order to make the file easy to find.
Then attach it to the email.
If you have any questions drop me an email.