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Is ignoring spam a bad thing?

I mean, if you just get the email and ignore it, then you've basically confirmed that your email exists -- there wasn't any mail delivery failure notice to the spammer, so obviously you received the email.

Isn't that enough to make you get more spam? Is it better to send a delivery failure notice, and if so, how would you make it look legitimate?

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closed as off topic by studiohack Apr 17 '11 at 1:39

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What makes you think that spammers get email addresses from "brute force" or something similar? They get email addresses from leaked/sold email databases. – apoorv020 Apr 23 '11 at 16:57
@apoorv020: They do the latter of course, but if is a valid email, then it would make lots of sense to try,, etc. – Mehrdad Apr 23 '11 at 19:17
up vote 7 down vote accepted

You assume that spammers actually care about replies. There is no reason to think they do. The only thing that counts is the number of clicks on the website they advertise. If there are a million more or less undeliverable message is irrelevant. This would drastically change only if sending an email would cost but a fraction of a cent.

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I would assume that they would rather send emails to valid addresses, right? So the goal here is to make your address look invalid. – Mehrdad Apr 16 '11 at 23:38
You have to look at it from an economic point of view: Sending 1 million more emails does not cost more than not doing so. The return per email is tiny - only a couple of apparenty uneducated hmmmm persons in a million do click on an spam link - even fewer do actually buy something there. Therefore, a spammer must send out as much as possible - you can't waste time checking individual answers. Hence, often, the reply adress or the from adress are not existant or reachable anyway. – Ingo Apr 16 '11 at 23:50
@Ingo: Just so I can get a feel for numbers, how many emails do you think a spammer can send in, say, a single minute? – Mehrdad Apr 16 '11 at 23:51
I doubt rather strongly that the average spammer even knows a given address exists. He has a database of them somewhere, which his software looks at in order to send the mail, and that's it. In fact, I would be surprised if the MAIL FROM: address were not entirely forged. So he likely wouldn't receive any reply either. (specifically targeted scams would be an exeption to this, of course, but they probably don't make up a large percentage of total spam.) – user55325 Apr 16 '11 at 23:58
The Rustock botnet was capable of sending an average of 192 spam messages per minute from a single infected machine. The entire botnet consisted of 150,000 to 2.400,000 machines. See – Wayne Johnston Apr 17 '11 at 0:13

Responding to spam provides some level of validation to the spammer that they are dealing with a valid eMail address, so not responding is actually better.

If you want to actually do something about spam, there are many options that range right up to being a full-fledged spam-fighter running SMTP [mail server] honeypots and DNS-based blacklists. To get started, I highly recommend that you read these two documents:

  How to deal with spam positively and professionally (passive and active techniques)

  The Rules of Spam

The biggest problem with spam is that spammers are completely ignoring your "natural right to consent" when they use your resources to foist their scams on all their innocent victims. Who pays for these resources, including internet access, electricity, equipment (including the extra wear-and-tear that spam causes), stress, and so on? If it isn't you, then it's whomever's home you're living in (and that makes them victims too).

At any rate, spam is theft because it depends on theft-of-service (unlike postal mail where postage must be paid in advance) -- if they had your consent to include you in their eMail list, then it wouldn't be theft because it wouldn't be spam.

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@Randolph: Your answer does not actually answer my question about the lack of delivery failure notification... – Mehrdad Apr 17 '11 at 1:20
@Mehrdad: Delivery failure notifications are typically ignored by spammers if they're generated at the SMTP Envelope stage -- the three-digit 5yz (500-599) error code that indicates an permanent failure has no effect on them because they will just try again in the future under the assumption that it may eventually work. If your mail server is generating a bounce back to them, then they'll just consider it to be confirmation that they're dealing with a valid account (but this bounce-generation approach is frowned upon because it tends to amplify spam). – Randolf Richardson Apr 17 '11 at 1:49
@Mehrdad: So, in short, either have your mail server respond with a 5yz code or just drop the connection altogether because these two methods will consume far less bandwidth. If your mail server can keep the socket open for a long time, that can slow down the spammer's "spamrun" a little bit. – Randolf Richardson Apr 17 '11 at 1:51
@Randolph: I'm confused... if they get a delivery failure, why would that tell them that my account is valid? Is this assuming that they don't inspect the contents of the reply? – Mehrdad Apr 17 '11 at 1:53
@Mehrdad: They don't have time to inspect delivery failure notices, but keep in mind that most spammers use "spamware" which is software that acts like a mail server and simply reveals to the spammer statistics about the number of 4yz and 5yz codes they receive (along with other overall information) -- for millions of stolen eMail addresses, they don't have the time to inspect every non-delivery notice (let alone a few dozen), plus they probably don't care anyway. – Randolf Richardson Apr 17 '11 at 2:53

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