Change E-Mail receipt Address in E-Mail-Notification according field content

Change E-Mail receipt Address in E-Mail-Notification according field content

Hi all,

I like to change the receiving E-Mail address of the E-Mail Notification according a field content.

Example:
the Notification receipt field should be filled with address xxx@xxx.com in case a Pull down Field is choosen content xxx 
or if the Content is yyy it should be filled with address yyy@yyy.com 

What is the name of the field in the Email Settings I have to address in the code?

Thanks in advance,
 Oliver