unfortunately, while the xml output method allows processors to use a
platform specific line ending while serialising, the text output method
doesn't say that they can, so you probably need to explictly output
^M^J pairs, ie
& # 1 3 ; & # 1 0 ;
(without the spaces which I added as apparently some mail clients prematurely mangle character references.

I'm using
(special characters not spaced; they are the same as above)

  <!DOCTYPE t:transform [
  <!ENTITY dos_line-break '&#13;&#10;'>
  ]>

  <t:document
      line-breaks="local"

meaning "create DOS line-breaks on Windows, Unix ones on Unix, etc".
Other values would be
  line-breaks="DOS"
  line-breaks="Unix"
  etc

--
http://www.pinkjuice.com/