Zoho Account eMails are not available to Zoho Desk eMail picker

Zoho Account eMails are not available to Zoho Desk eMail picker

Hi,

1. customer creates a ticket in Desk
2. Ticket gets forwarded to an agent
3. agent opens the ticket and replies to it using the build in mail function
4. agent wants to CC the reply to another Zoho user (e.g. sales) 
5. the agent must type the complete email of the sales person, not hint is given. In other applications within Zoho, you will get hints to faster find the required contact person at sales.

How can I configure this?