Acrobat DC uses your default system email address as your default address in the program as well. You can leave it as is, or add other email addresses.
When you choose a command, such as File > Send File > Attach to Email, you’ll see a warning message like this one:
Change the preference via this message, or by choosing Acrobat DC/Edit > Preferences, and choosing the Email Accounts panel. Add additional accounts, and choose a default email address. See details in the video: