How do spammers know they have a working email?

[Kojote]

I would like to know how spammers know if an email address is working or not? Surely, they won't just keep spamming the same email addresses, if they never get a response from the user. I personally use text mode in reading emails, so no web bugs can activate. I also report all my spam to spamcop, ftc, and my ISP. Yet, the same spam, with the same headers/subject line, is continuing. Different server IP's are being used by this spammer to send spam.

So do spammers not know good vs. bad addresses? You would think that they would have a database of addresses where they get no response. Otherwise, it is a very futile attempt they are making. Especially if an email address they are spamming, is no longer in use. They are just using up CPU cycles on the servers.

[Jeff G.]

The "servers" whose CPU cycles they are using up are zombies - why should the spammers care about zombies' CPU cycles?

[Wazoo]

It used to be that a million e-mails sent might get the infamous 0.008% return on some spam ... nowdays, with all the filtering, blocking, simple overloading of InBoxes, now it takes the sending of ten million e-mails to continue to find the clueless/idiots/whatever ... that's for the person actually looking for the gullible to send them money .... the other approach is the 'professional' spammer that offers "100,000,000 known good e-mail addresses looking for your stuff .... only $2,500 USD" ... guarantee is on the e-mail sent, not e-mail received/read ... neither case seems to offer a scenario for actually running a "clean" list ... both have poisoned the well for anyone 'respectable' trying to ease into e-mail marketing ..