Hi Mathias:

I can't manage to reproduce your problem. It looks like the regression 
tests do test this code path and your patch breaks all these tests.

The \n\n is correct as 'l' is a set of message sections separated by
blank lines, so \n\n terminates the last line in the previous section 
and adds a blank line.

What are the settings for these options in the mailgw section of your 
config.ini:

  keep_quoted_text
  leave_body_unchanged
  eol_re
  blankline_re
  sign_re

Thanks.

-- rouilj