do the Paragraph marks show up on the reciever end? I haven't used the "URL mail to" method but i usually build the body of the email into a text field and then use a calculation to put the pieces together. To test this I send then the email to myself to see what an end user might see. This at least gets me in the ballpark.
I hope this helps.
You have to URL encode the text for it to show up properly. %0D is the URL encode equivalent of a carriage return. You can use the GetAsURLEncoded ( ) function, or here is a handy reference: