smpt mail line too long -- How do I insert a line break

We are getting the error PMDF-SMTP-Warning: Lines longer than SMTP allows found and truncated. How do we resolve this?

thanks.

I was able to get it to work by putting environment.newline in the paragraph that was being built. It was a for loop that was building it and was html, so after every </tr> I put in an environment.newline.