The default email templates from CRM are not responsive (i.e. mobile friendly). If there is a lot of text phones will render the text as very small. A very unprofessional look.
A possible fix is to add "text-size-adjust" arguments to a css style call in the email <head></head> (we can't edit the head into in ZohoCRM emails.
p {
-webkit-text-size-adjust: 100%;
text-size-adjust:100%;
-ms-text-size-adjust: 100%;
}