My name is [xxxx] and I am a Pre-sales engineer for Zoho. Thank you for taking the time to contact us.
If you want to integrate your emails, you can do it using Zoho CRM within the One package. 
You can configure only one incoming email address to the application however, the outgoing email address can be multiple. 
I hope the above clarifies. Looking forward to assist you.

My previous reply was for the email integration with Zoho CRM where you can integrate only one incoming email address but multiple outgoing email addresses. Multibranding is a feature within Zoho Desk which will allow you to create multiple departments and set department specific emails and customer portals.

-Meerder mailadressen kan niet in het CRM, Projects etc. Hooguit om outbound te mailen, maar niet om te ontvangen. Zoho Mail kan je wel koppelen met je mails. Hierin zie ik dus wel een beperking eventueel. [translation: "Multiple mail-addresses is not an option in CRM, Projects, etc. At most outbound mailing, but not to receive from multiple emai addresses"]

I am sorry to say that it is not possible to have more than one email address/domain name in Zoho One. You can, however, send messages from more than one email address, but only outgoing mail.