How to change the automatic inserted E-Mail recipient when sending an email within potentials

How to change the automatic inserted E-Mail recipient when sending an email within potentials

Hello there, 

we are a marketing agency, that needs to communicate with the advertiser and the publisher. 
The problem is, if we want to send an email to the publisher within a potential, automatically the email of the advertiser is selected in the email window. It ist error prone to manually change that every time. 
How does Zoho define which email-adress to select in this window? Where am I able to change it?

Kindest Regards Moritz