> "\r\n" = crlf = windows linebreaks.

That's not necessarily the problem, though it would seem a likely candidate.

The problem might also be that you're viewing the contents of the email in an
HTML window, which formats sequential whitespace characters as if there were
only one space between tokens.

Where are you viewing the email?  Are you building an HTML email and reading it
in an email client, or are you just dumping the contents of the email to the
clients browser (i.e. echo()) to make sure everything looks good before
actually calling mail()?

nik