The email siphons are a real pita!
TAZ is the only server to actively deploy the front end rewrite rules that would trap them and redirect to a core 'no-harvest.pl' program that would send thousands of bogus email addresses...
SIX and NINE used to run the same until the extra overhead became too much... Every request the server was expecting was run through the rewrite rule, and of those maybe 1% were siphons... I could no longer justify the high expense of siphons slowing down the content delivery... Now there are a myriad of siphons on the market effectively compounding the problem by having to check for 20+ different siphons... Keeping up with all this eventually became detrimental to time and resources... The email siphons were also able to masquerade as legitimate browser Agents, and skating past the checkers...
Believe me, I was sadly dismayed when I finally had to deactivate the rewrite rules... It was the absolute last thing I ever wanted to do...
--Email Siphons should be handled like munitions--