How can I insert line breaks to my e-mail message?

A message could be sent as “Plain Text” or “HTML”. Use <br> tag if the content is HTML and n if the content type is “plain text”. For example, 

on add
 {
 on success
 {
 sendmail
 (
 To : zoho.loginuserid 
 From : zoho.adminuserid 
 Subject : "To insert line breaks" 
 Message : "Dear Customer, "+ "<br>Your order has been processed"
 )
 }
 }