Will unsubscribing from spam get you even more spam?

Question

To quote Rick's Spam Digest:

It’s just too likely that the spammer uses the “removal” feature as a means to compile lists of known-deliverable e-mail addresses, and you could simply wind up getting more spam for your trouble.

Phil Bradley actually did a little experiment (in 2002) and confirmed it:

I was soon to discover opting out of a mailing list is like wandering into the rapids just wearing a small life protector - you're going to get swept along very quickly and end up drowning!

I have never really doubted that unsubscribing from unwanted email will only result in more unwanted email.

But then I stumbled upon two articles that say it's a myth:

• Busting the Biggest PC Myths
• The 10 Biggest Spam Myths

Here is a discussion on the Straight Dope forum, with one user commenting:

Of course it's a myth. They send out many millions of spam messages a day, a high proportion of which bounce back. What do they care if you "prove" your address is real? They already have it.

My question:
Have there been tests (aside from Phil Bradley's) which confirm that unsubscribing from spam will result in even more spam?

Do spammers actually compile lists of "known deliverable email addresses"?

Answer 1

There have been several experiments that measure the effectiveness of unsubscribing from spam, which concluded in favor of unsubscribing.

For example, Kenneth Ladd Seldeen, a researcher with a Ph.D. in Biochemistry and Molecular Biology, has set up the following:

Used in this experiment were two web based email accounts. Email accounts were tracked for 45 days to determine normal levels of incoming spam email. One account averaged roughly 350 emails per day and after 45 days, unsubscribe links were clicked at a rate of 20 links per day. A second account averaged 3-10 emails a day and after 45 days all emails were clicked unsubscribe.

The results can be seen on his website, where Seldeen writes: "unsubscribing reduced average emails from 350 to about 80 per day, a decrease of nearly 80%."¹

Michael Dayah, a web developer from Knoxville, Tennessee writes:

I decided to test this hypothesis with one of the decade-old e-mail accounts on this domain, which received about 300 messages a day. On January 22, I began following every unsubscribe link in these messages. And I’m not talking about legitimate newsletters like NewEgg or MarketWatch, I’m talking about ShamWow and Acai Berry opt-outs. Within just a few days, the spam volume reduced to only 80 messages a day.²

Finally, the Proceedings of IFIP Summer School on Risks & Challenges of the Network Society from 2004 contain a paper by Swedish researchers, who write:

In a second experiment we investigated if unsubscribing to spam emails generated new spam. In all 219 spam were investigated and 182 of them allowed the user to unsubscribe. By transporting the spam massages to a newly-configured e-mail account with a "clean" environment it was possible to investigate the impact of unsubscribing from spam. During a four-week period we did not receive a single spam in return.³

1. http://web.archive.org/web/20140919123956/http://www.scientificameriken.com/spam1.asp

2. http://web.archive.org/web/20140919125112/http://essays.dayah.com/spam-unsubscribe-not-harmful/

3. Jacobsson, Andreas, and Bengt Carlsson. "Privacy and spam: Empirical studies of unsolicited commercial e-mail." In Proceedings of IFIP Summer School on Risks & Challenges of the Network Society. 2004.

Answer 2

The sites that you said addressed the myth might be working with spamming companies or be the spammers themselves. I don't know that much about spam, but it appears to not be the same as telling someone to take you off their mailing list when they call you.

Several other sites agree with the fact that you should not unsubscribe from spammers as it does the following-

The typical advice from anti-spam groups is to not even try to use their "unsubscribe" methods, since that confirms for the spammer that the address is not only good (thus: send it more spam!) but also that the recipient actually opens spams sent there (thus: send it even more spam!) http://www.spamprimer.com/spammers_wont_unsubscribe_you.html

Also, from this we can see that people have done other test for this.

This qoute outlines that clicking unsuscribe is the wrong course of action.

Before you answer, in most cases the spammers are just guessing at email addresses. Fill out the ‘unsubscribe” line, and the guesswork is over: they know they have a live one. Worse, said Maiffret: "In reality, that's usually an indicator to increase the level of things they send to you. We even see when you click unsubscribe, it'll take you to a website and the website will actually try and attack against your computer," he explained

Filipiak had to change his email address, as this reporter will also have to do. For this article, I clicked "unsubscribe" on two weeks’ worth of spams; more than 125 times. My daily spam average is on the rise, with no signs of slowing down. With spam accounting for an estimated 80 percent of all email traffic in the United States, the spammers don’t appear to be slowing down, either. The best option, experts said, is to choose the "Mark as Junk" option provided by some email providers. If that’s not an option, just hit "delete" and move on.

As for "Do spammers actually compile lists of "known deliverable email addresses"?" I couldn't find any info to support that, but from the volume of mail these people were sent other spammers were probably in on it.

I did however find numerous accounts of people's e-mails sending other people spam, which if they unsubscribe can give the spammers more accounts. I found this by googling "unsuscribing to spam gets you more spam"(the results were to many).