The non-commercial  version of Ricemail  has a known problem  whereby, if
you  forward a  message  whose  header has  lines  longer  than 80  bytes
(typically,  a  "Received:"  line),  the  forwarded  header  contains  an
incorrectly folded version of the long  field which results in the syntax
error you  are observing. I  don't know of any  straightforward solution,
other than TELL MAILER SET PUNCH, which  tells LMail to fold all lines in
your message  at 80  bytes. But of  course this means  you can  no longer
receive messages with long lines.
 
  Eric