The organizers of the Email Technology Conference, which kicks off in San Francisco tomorrow, said that Scott Richter, CEO of spam outfit OptInRealBig.com LLC, and Julian Haight, founder of SpamCop, have withdrawn from the event.

Unfortunately, both parties scheduled to appear in The Great Debate: Email and Free Speech have been withdrawn by the ETC board due to issues stemming from their upcoming lawsuit, the show’s organizers said in a statement.

Richter sued SpamCop’s owner, IronPort Systems Inc, earlier this year, claiming SpamCop’s spam blacklist blocks OptInRealBig’s email from getting through to people, interfering with its contracts with advertisers.

Richter himself, recognized by anti-spammers as one of the world’s most prolific spammers, is being sued by Microsoft Corp and New York attorney general Eliot Spitzer over allegedly deceptive tactics used in the spam sending.

That suit relates to 2003 spam. Richter now claims that his spam is compliant with the US CAN-SPAM Act, which forbids spammers disguising their identities and forces them to allow recipients to opt-out of future mailings.