The "Date" header is required by rfc822 and one cannot
always rely on  the MTA to insert this header.  Mails
sent by Roundup are missing this header.

A one liner in "send_message" in roundupdb.py should do
the job:

 writer.addheader('Date', time.strftime("%a, %d %b %Y
%H:%M:%S +0000", time.gmtime()))