Pre determined Content of Email Body

Just a small how-to question. I have received emails that not only contained predetermined content, which is simple enough to set up, but also contained content I could not manipulate. Spaces were indicated where I was to put in information. The information couldn’t go anywhere else, except where indicated.

It functioned something like a form, but did not have the appearance of a form, as I am accustomed to seeing them.

I need to know how this is done. If anyone has this info, I’d be appreciative of it.

Many thanks,
Marcia Mulloy