Change the predefined email adress for answering tickets in Zoho Desk

Change the predefined email adress for answering tickets in Zoho Desk

How can we change the predefined email adress for answering tickets in Zoho Desk? 
How can we asign different email adresses to diferent groups of Agents?
Is it possible to autoselect the predefined email adress depending on a particular field of the ticket?