Regular users retry, that's the point of temp-fail on first attempt. Botnets never retry because they aren't real mailers with send queues. And the number of pe

Regular users retry, that's the point of temp-fail on first attempt. Botnets never retry because they aren't real mailers with send queues. And the number of people who have ever intentionally operated a mailer from a Windows XP box on a residential ADSL line is very accurately approximated by zero.