Mailing lists and sa-exim

I'm running into a problem with sa-exim and Mailman in that sa-exim  
(exim 4.63) is expanding the list of recipients so that I'm getting in 
the headers the following line:

X-SA-Exim-Rcpt-To: followed by every member of the mailing list.  How do I suppress this?  How do I suppress most if not all the extra header additions that sa-exim (and for that matter SpamAssassin) add?

TIA

Jeff