At some point, a long "Received:" header is being incorrectly folded. The
field is split into two lines, but  the second line does not start with a
space or  tab, and so  syntactically it constitutes  a field on  its own.
Unsurprisingly  it is  an invalid  one, and  LISTSERV stops  scanning the
header at that point. You would have to identify the bad gateway and have
it fixed.
 
  Eric