[exim] Which other services do this?

So Craigslist will send you mail and they will hide the identity of
you and the buyer

hence

if foranyaddress $header_to:,$header_cc: ( ${domain:$thisaddress} does  
not match
  ^elastica.com\$ )
then
    logwrite "mail header_from $header_from: header_to $header_to:"
endif

shows up quite a lot in my for spam but previously I was throwing this
stuff away and hence losing responses to craigslist postings.

Does anybody know which other services send you mail like this?