There are two passwords required for email integration - one is the Zoho password, the other is the email password. Zoho Admins don't have access to Users passwords, nor do I or Zoho. The primary reason is security to prove that someone did something on the CRM system. If I had your password, I could delete accounts and it would look like you.

What you can do as an Admin is go to Setup (in CRM), Channels, Email, Email Sharing. From there you can see who has enabled Email Integration, If it is Public / Private (this you can change), What domains are excluded (again you can change these) and who the emails are shared with. From this you can send out a gentle mail - Do you need help with Email and Calendar integration?

It is good for the Users to know how to change this as if they have a password reset they would need to change their password in these locations.