Since FileMaker only creates plain text emails, this may be a challenge unless you acquire an email plug in where you have more options.
In straight Filemaker you could do this:
Define a text field and place it on a layout that users do not have access to. Then use a script that:
Finds/sorts the records you want in the email.
Do this on a layout designed to list only the fields you want in your email.
Uses Copy All Records to copy the found set of data to the clip board
go to the layout where you put this new text field and paste the clipboard contents into it.
Now use Send Mail with a calculation expression for the message body that includes this text field.