Sending Emails from Activities

I am trying to send an email from ZOHO when I am going through my daily activities.
I created a template with record type 'leads' which has a subject, body and attachment.
When I click on the green 'Send Mail' button, a mail window pops up with the contact email address in the 'To' field.
I select Add Template and select my template from the drop down.
This fills in the subject, but the body is blank and I'm not even able to type in a message.
Clicking on the Send button has no response.
No clue how to proceed.
Any help is appreciated.
Thanks