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"
)
}
}