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Hotmail & Yahoo Mail Using Secret Domain Blacklist 345

Frequent contributor Bennett Haselton writes: "Hotmail and Yahoo Mail are apparently sharing a secret blacklist of domain names such that any mention of these domains will cause a message to be bounced back to the sender as spam. I found out about this because — surprise! — some of my new proxy site domains ended up on the blacklist. Hotmail and Yahoo are stonewalling, but here's what I've dug up so far — and why you should care." Read on for much more on how Bennett figured out what's going on, and why it's a hard problem to solve.

On December 7th I sent out a normal batch of emails to the Circumventor mailing list, where I send out new proxy sites for getting around Internet filters. I registered seven new domains and sent each domain to one seventh of the list; the list contains about 420,000 addresses, so each one went to about 60,000 people. (Each new site is only sent to a random subset of the list, so that a blocking company can't just subscribe one address to the list and block all new sites as soon as they're mailed out.)

The list is also comprised of 100%-verified-opt-in addresses, meaning that a new subscriber has to reply to a confirmation message in order to be added to the list. That's considered the gold standard for responsible mailing, but major email providers keep finding new ways to block the emails as "spam," which sometimes provide interesting insights into how the filters work behind the scenes.

After the last mailing, for example, all of my newly registered domains got disabled by the registrar because two of the domains had been incorrectly blacklisted by the Spamhaus Domain Block List. It took two days to discover the problem and then several hours to trace the problem to Spamhaus, although once I found Spamhaus's automated form I was able to get the domains un-blacklisted immediately. So the registrar re-enabled the domains a few hours later, although the traffic to the domains never returned to its previous levels. Spamhaus, meanwhile, continues to claim the DBL is a "zero false-positive" list, and has yet to acknowledge the error or contact me to help get to the bottom of how it happened. Well, they know how to reach me.

At least this time around, my domains didn't get disabled. Instead, the messages rolled out for a few hours with no problem (replies from users indicated that at least some and users were receiving them), until bounces abruptly started coming in from and addresses saying:

----- Transcript of session follows -----
... while talking to
>>> DATA
<<< 550 Message Contains SPAM Content
554 5.0.0 Service unavailable

After pummeling my address with bounce messages (to the point where my own Gmail account started bouncing because it was getting hammered with so many bounce messages from Hotmail and Yahoo), when the dust finally settled, I tried reproducing the error by sending test messages from my server's IP address to a test Hotmail account. It turns out that out of the seven different URLs that I had been mailing to our users, four of the domains in those URLs would generate a "550 Message Contains SPAM Content" error when sent from my IP to a Hotmail address, and the other three did not. The message didn't have to contain the banned domain in the From: address; the message would get blocked if it even mentioned the domain anywhere in the message body. (This only happened when sending from my own IP address at It didn't happen if I tried sending a message from my Gmail account to a Hotmail address, even if the message contained one of the four banned domain names, so the issue probably won't reproduce if you try sending a test message yourself.)

But interestingly, Yahoo Mail started bouncing my messages at about the same time — out of the seven domain names, the same four domain names were being bounced by Yahoo Mail as by Hotmail, also with the error "550 Message Contains SPAM Content." That's far too unlikely to be a coincidence, so it looks as if Hotmail and Yahoo Mail are using a common secret blacklist of domain names that cause a message to be blocked as spam. (As it happens, the other three domains were also being bounced by Yahoo Mail with the error "Message Contains SUSPECT Content" — as opposed to "SPAM Content" — while those three domains were not blocked by Hotmail at all. That of course is aggravating, but the real clue lies in the fact that both Yahoo Mail and Hotmail were giving "SPAM Content" errors to the exact same subset of domains.)

I don't want to publish the list of all seven domain names here, so as not to make it too easy for censorware companies to block them all, but one of the four blacklisted domains was '' (All of the new domains I register are nonsensical two-word combinations, since those are the only .com domains that are likely to be (1) still available and (2) easy to remember.) As soon as it seemed like Hotmail and Yahoo Mail were working off of a common blacklist, I checked to see if Spamhaus had screwed up again and listed our domains, but none of the seven domains were on Spamhaus's lists.

I looked up on the service, which checks against all major spam blacklists, but no hits were listed there either (except for on some defunct services which haven't been updated in years).

So if Hotmail and Yahoo Mail are both using the domain blacklist, perhaps it's a list compiled by one company and then licensed to the other, or perhaps it's a third-party list not widely known to the public. (Hotmail uses their own SmartScreen filter, but I've found nothing online about Yahoo using it as well.) It's conceivable that one or more of the domains might have gotten blacklisted as a result of Hotmail or Yahoo users clicking their "This is spam" button. However, Hotmail allows newsletter publishers to view data about what percent of their messages to Hotmail users are being flagged by users as "spam," and when I looked up the stats for our IP, they showed a "complaint rate" of less than 0.1% (usually the rest of people hitting 'Junk Mail' to unsubscribe from the list). Assuming that the complaint rates are similar for Yahoo Mail, it's unlikely that the domains got blacklisted as a result of user complaints, unless the blacklist trigger has a ridiculously low complaint threshold.

Neither the Hotmail postmaster site nor the Yahoo postmaster site mention anything about a list of domain names that could cause a message to be blocked for mentioning the domains in the message body. Yahoo Mail does provide a support form for newsletter publishers to send inquiries about why their mail is being blocked; I submitted that on Saturday and started a thread with email "support," although so far their response has just been to copy and paste articles from the Postmaster site, with tips like "Send email only to those that want it." Each time, I reply saying, No, this is not the problem, the problem is that the domains in the messages are getting incorrectly blacklisted, and each time, support cheerfully sends me another article. If I'm not literally talking to a bot, I might as well be.

I opened a similar ticket with Hotmail, and they sent me a form letter saying that the emails were being blocked because of SmartScreen, and that as a matter of policy, they would refuse to fix any errors being made by the SmartScreen filter. Waiting to see if I get a reply from a human next.

So why should you care? Well, for one thing, if you care about users in China and Iran being able to receive proxies to get around their Internet blockers, right now Hotmail and Yahoo are thwarting these proxies more effectively than those countries' own censors are. Yes, these are real people who really do write back to me after a mailing goes out, telling me about how they were able to use the proxies to receive banned political information, and sometimes how long the proxy lasted before the censors blocked it. This week, they had to do without.

But more importantly, this is an example of a general problem: That there are certain types of issues, like blocking of legitimate mail by spam filters, where the "free market" does not deliver the best experience to consumers, and the costs get passed on to everybody. Sometimes the problems could be solved with some effort, but the effort does not get made, because people believe that the free market will solve the problem, or that it already has.

In theory, if consumers have enough information about different companies and their services, the companies can compete to provide the best product to users. The problem is that if one type of information is systematically hidden from users — in this case, the fact that their mail provider is blocking mails from reaching them — then the "theory" falls apart. Since spam getting into your inbox is a visible problem, but missed email messages are an invisible problem, Hotmail's incentive is not to give the user the best experience, but rather to err on the side of blocking legitimate messages — even if the user might prefer to get slightly more spam, than to miss one important email that they were waiting for.

This means we're not just talking about a few messages getting caught in filters, which could happen even in an efficient marketplace. We're talking about a permanent equilibrium where the user gets a sub-par experience by default — a trade-off that causes them to miss more messages than they want to — and senders have to pay the cost of overcoming the marketplace inefficiencies. (Which means if the sender is a business you buy from or a charity you support, the costs get passed on to you.)

Pretty much the entire financial cost of sending email, is attributable to the failure of the "free market" to motivate email providers to deliver non-spam emails into their user's inboxes. If a company or organization uses an email list hosting company like AWeber or Constant Contact to email their users, they pay a fee of about $1 per month for every 100 users on their list (which would run me about $4,000 per month). That fee doesn't go towards bandwidth — even a 1-million-subscriber list, emailed once a month, would use less than 3 GB per month of bandwidth, which is what GeoCities was was giving away for free 10 years ago. What you're paying for is the fact that AWeber and Constant Contact have friends in the right places at Hotmail, Yahoo, and Gmail, so if your mails are getting blocked, they know the people to call to fix the problem. If you run your own list instead of paying a hosting fee to AWeber or Constant Contact, you'll end up paying other costs indirectly, through loss of income when your messages don't reach recipients, or in time and money spent trying to fix the issue. (I have to take this option anyway, since I send different URLs to different random subsets of my list, which is not supported by AWeber or Constant Contact.)

On the other hand, if the market actually "worked" — if email providers did reliably deliver non-spam messages to their users — a company or charity could run their own list for virtually zero cost, and would be able to keep all of that money. (I incur no up-front fees for running my own list; all of the costs are the time spent trying to get Yahoo, Gmail, and Hotmail to stop blocking it.) So every time you donate to a charity or buy from an online retailer, a little bit of that money goes towards the cost of that organization having to fight past marketplace failures in order to get their email to you.

I don't think there's an easy algorithmic solution, like crowdsourcing Facebook complaints or using random-sample voting on Digg. Generally, I just think we need more awareness of the fact that, under certain conditions (including those surrounding email deliverability), the "free market" is virtually guaranteed to arrive at a non-optimal solution. One manifestation of that awareness would be if Hotmail, Yahoo Mail, and Gmail created public points of contact where legitimate email publishers could find out why their emails were blocked, and had real humans responding to the messages and fixing the problems. By default, the imperfect information in the marketplace leads toward an equilibrium that errs on the side of blocking too much legitimate email, so anything that pushes the equilibrium back towards more legitimate messages getting delivered will improve the experience for users and lower costs for senders.

Besides, there's a more basic ethical issue here. If you're Hotmail and you tell your users that you're providing them with "email accounts," then those users expect those accounts to work — including having the ability to receive mails from mailing lists that they've signed up for. Helping legitimate emails get through to users is not just a matter of addressing a marketplace inefficiency, it's a matter of honesty.

Larry Lessig's book "Code is Law" describes how default choices built into the architecture of the Internet and other environments — the "code" — can steer our behavior in ways that we might not choose otherwise. I'm making essentially the same point in saying that some problems are not fixed by market forces, because people are not aware of the problem at all. I think the evidence and the reasoning are straightforward in this case, but it's hard to convince people who have adopted it as an axiom that whatever the free market arrives at, must be the solution. My favorite single sentence in Lessig's book was, "Put your Ayn Rand away." I could imagine the years of pushing against dogmatic fanaticism that led him to write that sentence, and I knew how he felt.

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Hotmail & Yahoo Mail Using Secret Domain Blacklist

Comments Filter:
  • Summary (Score:5, Insightful)

    by sorensenbill ( 1931240 ) on Thursday December 13, 2012 @01:20PM (#42275493)
    Is there a summary of the summary available?
    • Is there a summary of the summary available?

      We call them "titles"
      Here's one example: Hotmail & Yahoo Mail Using Secret Domain Blacklist

      • I wouldn't be suprised if it's just Bayes. The majority of messages with links leading to those registrars' domains were categorized by human readers as spam, so automated bayesian analysis picked it up.

        As long as you have Internet governance that is primarily concerned with eliminating certain forms of political speech (Great FireWall of [insert name of nation here]) rather than ensuring a free market and fair trade, you're going to have this problem. The same low-rent registrars are going to be used fo

    • Simple summary (Score:5, Informative)

      by Pollux ( 102520 ) <{ge.ten.atadet} {ta} {reteps}> on Thursday December 13, 2012 @01:41PM (#42275909) Journal

      He's saying that Hotmail, Yahoo, and GMail are running a cartel of free online webmail services.

      He's trying to get opt-in email to accounts on these systems, and it's not going through. He has evidence indicating these services operate a common hidden blacklist service keeping those emails from getting to the accounts. He cannot reach people within these organizations to open up emails coming from his domains, as he does not have an inside contact to "assist" him with this problem. This leads him to speculate that Hotmail, Yahoo, and GMail are operating like a cartel, where only "approved" email list hosting service companies with inside contacts are able to do business with these services.


      • Re:Simple summary (Score:5, Interesting)

        by niiler ( 716140 ) on Thursday December 13, 2012 @01:53PM (#42276117) Journal
        Bingo. Good summary. I gave up using my own server to send email a couple of years ago for precisely these reasons. It wasn't worth trying to get de-blacklisted every few weeks because my server had an obscure domain name. If I recall, when I sent out more than 10 emails in a batch (we're talking maybe as many as 30) to members of a class, this triggered the anti-spam bots. When I did it from gmail or from other major providers, things worked beautifully. I had too many irons in the fire to deal with this, and while I would love to use my own server's email capability, it's not worth it anymore.
        • Re:Simple summary (Score:5, Insightful)

          by marcello_dl ( 667940 ) on Thursday December 13, 2012 @02:48PM (#42277163) Homepage Journal

          > I gave up using my own server to send email a couple of years ago for precisely these reasons

          In fact, that's probably what the cartel wants, ultimately.

        • Re: (Score:3, Insightful)

          by Anonymous Coward

          Or, you could just keep using your server as before. People who use providers which block your server could wise up and use something else, rather than let Google harvest all their email for marketing purposes while sometimes letting them see an email they want to see.

          When you switch to Google, you become part of the problem.

          • This is weird... I don't think Google was mentioned in the summary at all.

            But regardless, they're not operating with a list of approved senders. I build my own systems and send mail through them all the time. Sometimes just regular mail service, some for mass emailing (legally and legitimately). You'll have to take my word that I don't have super-secret inside contacts at Google, Yahoo and Microsoft to make sure this works.

            Now if you meant to say they have anti-spam filters that occasionally throw false-pos

      • Yes, now let's see if someone at dice can replace the article with this actual summary!
    • No, but I can summarize the summary of the summary: People are a problem.

    • Spamhaus != 0 false positives. This guy sends the same email out to tens of thousands of people who tend to use Yahoo or Hotmail. They both block the messages as spam.

      Just FYI, I seen this guy bitching about it MONTHS ago. Apparently he still hasn't made a lot of headway. However, if you operate like a spammer (sending the same email to multitudes of folks, while relaying information about open proxy servers as information), then you will be treated like a spammer
      • Re:Summary (Score:4, Insightful)

        by afidel ( 530433 ) on Thursday December 13, 2012 @02:38PM (#42276993)

        Why? By definition he is NOT a spammer since his messages are neither unsolicited nor commercial. It should be fairly easy for the responsible parties to verify he following best practices and whitelist him but apparently that's too much work for the postmasters at the big 3 webmail providers. Basically the postmasters at yahoo, gmail, and hotmail aren't doing their jobs. I know if our email admin was so bad at rectifying false positives he wouldn't be here for long but because of the scale of these organizations that pressure isn't happening.

        • As a consumer of email, I would rather the 1% find a better way to communicate rather than stupify the email system even more to accommodate them
          • Re:Summary (Score:5, Informative)

            by afidel ( 530433 ) on Thursday December 13, 2012 @03:09PM (#42277503)

            Why? Listservs are older than SMTP and have always been one of the use cases for electronic communications. Plus it's not like those providers are blocking all listservs, just those that don't pay their friends stupid high monthly fees for the privileged of emailing their users.

    • yeah: guy discovers cloudmark domain blacklist is used by two cloudmark customers. At least, that's my opinion. this information isn't new, this list has been around for years, and you don't get on it easily. It takes multiple reports from multiple accounts before they add you.

    • by genner ( 694963 )

      Is there a summary of the summary available?

      It's a pain in the butt to get yourself removed from yahoo's email blacklist.
      The end.

  • I could maybe see their necessity 10 or 15 years ago, but statistical classification techniques are good enough these days that a blunt tool like a domain blacklist doesn't really make much sense. Heck, Paul Graham was arguing that seven years ago [], and it hasn't gotten less true.

    • Blacklists are nice because they reduce server loads. Sure, running a statistical classifier for one user is not so hard, but if you have to process hundreds of millions of messages per day, that is a lot of CPU time spent on spam.

      Now, I agree that blacklists are bad, but we do need some system that doesn't require large amounts of CPU time or other resources. Hashcash is interesting here, in that the CPU time is mostly spent by clients; one might be able to slow spam down enough to let a combination o
      • Blacklists are nice because they reduce server loads. Sure, running a statistical classifier for one user is not so hard, but if you have to process hundreds of millions of messages per day, that is a lot of CPU time spent on spam.

        The CPU time spent on running something like SpamAssassin is insignificant compared to the bandwidth, disk writes, etc., caused by spam. Keeping the incoming e-mail in a RAM disk until you have truly accepted it for delivery (which isn't dangerous even if the server crashes hard) is the #1 thing that speeds up e-mail intake. At that point, scanning takes almost no time.

        As you mention, though, greylisting does the best job of keeping your overall load down, since you don't even need to use network bandwidt

      • but we do need some system that doesn't require large amounts of CPU time or other resources.

        Why? CPU time is dirt cheap if you can concentrate your task. The bandwidth (a much scarcer resource) is already being spent, and better decisions will just tend to reduce your costs there. To me this smacks of laziness, not efficiency.

    • The spammers have found various ways around these. Often they throw a bunch of the "high target" key words (e.g. viagra, cialis, penis enlargement) in as images, or they'll use computer generated text that looks somewhat real enough to even fool some human readers in order to throw off those filters. This works because the more words you have, the less likely the small terms will be snagged.

  • by Anonymous Coward

    The only treatment is a deadly poison that you hope kills off the bad parts before the good suffers too much.

    • Part of the problem with spam fighting is that we are not distributing the spam fighting load. Hashcash distributes the load somewhat, in that it forces spammers to use more resources to send out their message and can slow them down somewhat. A distributed filtering system that allowed people to volunteer CPU time and bandwidth to filter spam (with some system of gaining the trust of an email server) might also work; imagine if hundreds of millions of people were relaying / filtering 100 messages per day.
      • by afidel ( 530433 )

        There are several distributed reputation filter systems but they are all commercial AFAIK.

      • Hashcash distributes the load somewhat, in that it forces spammers to use more resources to send out their message and can slow them down somewhat.

        Unfortunately, until you get to a significant number of bits, hashcash doesn't take all that long to compute, and you can pre-compute them.

        I use 23-bit hashcash on all my outgoing e-mails, but if the address has been sent to before, there is likely a pre-computed 25-bit hashcash waiting. I use idle server time to pre-compute for any address that has been sent to from my servers. Since the hashcash expires in 25 days, I don't have to do this very often unless the recipient is a frequent one. Then, to keep

  • What's with the gratuitous complaints about the "free market" not giving some mythical "optimal solution" that lets you send your "100% guaranteed opt-in" spam without interference? I call bullshit. If Hotmail isn't accepting your "really honest it's not spam" mailing list stuff, maybe you should try contacting them about it. The "free market" doesn't magically solve problems without people doing what it takes to address the problems.

    • The problem with most be free email providers IS contacting them. You're not paying them, so they don't give a shit. Hell Google is hard enough to get a hold of when you are paying them.

      The second problem is spammers lie about everything. This has turned server operators on to the line of thought that 'everyone is a liar'. If you weren't a spammer you wouldn't have been blocked in the first place. Needless to say this causes a number of race conditions.

      And yes, I do run outbound and inbound SMTP services fo

    • by c_sd_m ( 995261 )
      He did contact Hotmail about it. He got a form letter response, replied again and hasn't heard anything. Yahoo keeps just sending him generic, irrelevant articles from their knowledge base. Neither company is "contact-able" in any useful way.
  • by Anonymous Coward on Thursday December 13, 2012 @01:41PM (#42275911)

    Are the proxy servers you are sending out on these lists capable of relaying mail onwards on port 25? If so this is probably a significant factor in these blacklistings. If you block outbound connections to port 25 when you set up these proxies, you'll probably find your blacklist problems are significantly reduced.

  • by joostje ( 126457 ) on Thursday December 13, 2012 @01:43PM (#42275959)
    Yes, verified opt-in is one requirement. But if you don't want to be marked as sender of SPAM, you should also make it *very* simple to unsubscribe. I know I've subscribed to a few lists, and at first read the emails, then ignored them, and eventually thought "should unsubscribe". But if that unsubscribing is difficult, I'll just hit "spam" in gmail (or whatever). I don't see the emails and more, and the sender gets blocked as spammer.
    • by magic maverick ( 2615475 ) on Thursday December 13, 2012 @02:13PM (#42276539) Homepage Journal

      Here's the latest email I got from Mr Haselton (with the email addresses changed though).
      It's apparently very easy to subscribe. (Though it's not one click as you do need to enter your email address if you use the webpage option.) Is that good enough for you?

      From: Bennett Haselton at <>
      Reply-to: "Bennett Haselton at" <>
      Subject: new Circumventor, in a new format
      Date: Fri, 07 Dec 2012 04:00:02 -0500 (07/12/12 10:00:02)

      [You are receiving this because you subscribed to the Circumventor distribution list.
      To unsubscribe from this list, click here: []
      or reply with the word "unsubscribe" in the subject.]

      Happy Holidays everybody -- your early Christmas gift enclosed: []

      This Circumventor site is in a different format but it should work as well as the others. You *must* access this one with 'https' at the beginning of the Web address; it won't work with 'http'.

      You can attempt to access the "regular" Facebook through this one, for example, but it might not work correctly; the most reliable way is to enter [] on this Circumventor site, which will take you to mobile Facebook. Unfortunately Youtube still isn't accessible yet but we're working on it.

      Don't waste too much time on those school computers - Santa's watching!



      "When I was in high school these twins got mono. They got stereo." -Demetri Martin
      14615 NE 30th PL #10D, Bellevue WA 98007/blockquote.

    • I'm on this particular mailing list, so I can confirm that he makes unsubscribing quite easier. Easier than any other list I've ever been on in fact. Every email has the following text as the first paragraph:

      [You are receiving this because you subscribed to the Circumventor distribution list.
      To unsubscribe from this list, click here: []
      or reply with the word "unsubscribe" in the subject.]

  • I could swear this same guy was complaining about problems with his "I swear it's not spam" mailing list several months ago.

    • by ADRA ( 37398 )

      Sounds like the same guy. At least the exact same scenario...

      • by czth ( 454384 )
        No - that was about Spamhaus (which is mentioned again in this current writeup but not the main point); this scenario is about Hotmail/Yahoo! having (he believes) a shared secret domain blacklist that applies to the content of emails.
    • Re:Is this a repeat? (Score:4, Informative)

      by Bill Dimm ( 463823 ) on Thursday December 13, 2012 @02:02PM (#42276339) Homepage

      Yep, 2 months ago []

    • by PRMan ( 959735 )
      Before, he complained about the problem. Now, he is sharing what he found out.
    • Hence the words "frequent contributor" at the top.

      I've been using his service for at least six years. It's as far from spam as you can get. Certainly far less spammy than the emails from newegg or Amazon (which is among the worst!) or any of the others that have no problem at all getting through spam filters. Multiple ways to unsubscribe right at the top of every message, verified opt-in, low volume, no embedded tracking features (all plain text), and legitimate content.

      So what the hell else do you want? Sh

  • I used to work security at a major hosting provider. If we got complaints about your mailing list, the first thing we'd do is ask you about how you got your list, to see if it complied with our requirement for verified opt-in lists only. We'd also sign up ourselves or check logs and code, because customers always lie (except when they don't).

    Right now, I'd apply the same standard of skepticism. I understand that revealing such things would make your proported aim of censorship circumvention hard, but I'd st

    • Been on the list since late 2005 and I never delete an email, so I can confirm.

      You subscribe at his website and you get a confirmation request email. You confirm, and it sends another message confirming that you've been added. The content is legitimate, the volume is fairly low, every email gives two unsubscribe methods in the first paragraph of the message (click a link or reply with unsubscribe) and all messages are plain text.

  • Even S/MIME might meet your needs in this case. Encryption is cheap enough even for mailing lists now.
  • by Anonymous Coward on Thursday December 13, 2012 @02:16PM (#42276591)

    Early on (before I quit reading) the OP said:

      It turns out that out of the seven different URLs that I had been mailing to our users, four of the domains in those URLs would generate a "550 Message Contains SPAM Content" error when sent from my IP to a Hotmail address, and the other three did not. The message didn't have to contain the banned domain in the From: address; the message would get blocked if it even mentioned the domain anywhere in the message body.

    It seems to be treating his email as spam even when he sends one email to a single address.That isn't spam.

  • Ironic. Almost all blacklist providers keep proxy sites on their default "bad sites" list. Were I running URLBlacklist or similar, I would simply sign up for his email service and make a point of adding every web domain spotted in his emails. Almost an instant kill for the blacklist provider; by the time email recipients can act on the information, it's already been blacklisted.

  • How in the world did it take you two days to figure out Spamhaus was blocking your stuff?

    Save yourself some time down the road and just go to Enter the domain name it and can check all kinds of things for you. If a list is blocking it, you can get details as to why. In the past I've seen various reasons, but most are pretty detailed and provide quick access to the forms you need to get removed.

    As for your idea of a secret shared blacklist between hotmail and yahoo, it sounds more like it's

  • Preface: I am not taking the side of the spammer here. You keep that shit out of my inbox, fucker.

    That said, the real issue is the censorship of people's messages without their knowledge or consent. Granted, nobody wants to have to filter through millions of V1@gr@ ads just to read their mail, but on the same note, nobody wants someone else going through their mail and arbitrarily deciding what will and will not be delivered. I understand the purpose of the spam filter, and am glad it's there - but a sec
  • by Khopesh ( 112447 ) on Thursday December 13, 2012 @04:50PM (#42279259) Homepage Journal

    Ironically enough, you can isolate the "moles" by listwashing [], just like spammers do for spam traps.

    You've already started the process: you know that three sevenths of your subscriber base is probably safe. In your next run, make sure each of the remaining four groups is subdivided again. Each time you find a group that isn't a mole, you've reduced the potential mole list. Eventually, you'll have just a few accounts and you can silently drop them from your service (or confront them, your call).

    There was also an earlier comment on spammer abuse of your proxies [] that I'd like to expand upon. While it asks you about proxying port 25, there's also the potential for abuse with respect to port 80/443: 419er []s are increasing their use of proxies to hide their identity from free webmail providers so they can get free passes on sending spam. If you're better at cracking down on them (by e.g. blocking access to yahoo and hotmail on your proxies), you'll probably have better luck overall.

    Maybe you can combine the above two ideas: groups of subscribers known to contribute to getting blocked will get domains whose proxies can't use freemail.

MESSAGE ACKNOWLEDGED -- The Pershing II missiles have been launched.