When emailing someone from a contact, Zoho has different behavior depending on whether you click the actual email address field within the contact information, or whether you click the 'Send Mail' button in the email section of the contact details.  Clicking the email address brings you into Zoho mail where you don't have (1) the ability to use a CRM template or (2) you don't have your CRM signature (aka you're using Zoho Mail).  When you click Send Email, you get a pop-up within the CRM, thus allowing you to use templates and signatures (aka you're using Zoho CRM-email).  Both of these cases should create the same behavior (opening the Zoho CRM-email pop-up). 

Which brings me to my next point: your Zoho CRM signature, should be your default signature within Zoho mail.  We use dynamic fields for our signatures so at the least, you should be able to select your CRM signature when replying from Zoho Mail.

I understand the email/CRM integration is relatively new, but focusing on consistent behavior will greatly increase user adoption.

Thanks-