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when I got up this morning I found more than 300 emails in my mailbox with numbers growing by the minute. ALL those mails were bounce mails coming from Russia.

Looking at the attached original mails I noticed that the "From"-Header is set to an email address that routes to my mailbox. At first I feared that someone has hacked my mail server, abusing it to send spam and I get a lot of bounce mails now, but I can't see any hints in the mail headers, that those emails have actually passed through my server. It looks like someone just uses this email address of mine as sender of spam mails and lots of email servers reject those mails, sending bounces to me.

But what can I do about it? Ok, shut down this particular email address that is not very important to me anyway, but in the long run, somebody may use other addresses that I don't want to shut down. With the help of Google I found many other people having the same problem, but unfortunately no solution :-(.

I am running Exim as mail server.

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Unfortunately, you most likely cannot do anything about this. The good news is that you have not been hacked.

Despite my job as a professional IT guy, I knew a man, 25 years my junior, through chess tournaments, who was one of the world's most prolific spammers (before the CAN SPAM law) until AOL sued him out of business. I got the rare opportunity to see how a major spamming operation works, and frankly it was quite amazing. It also gave me great insight into how they operate, although I am sure it has evolved a lot since, although not for him.

He had a T-3 and 40 more 1Mb DSL lines all pumping out millions of SPAM messages daily (250,000/hr 24/7). One of the things spammers do is spoof headers, meaning they say that it is coming from anyone they like. I do a lot of e-mail server work, and part of what I often have to do is test e-mail using Telnet. I put in the e-mail commands line-by-line, and as part of that, I could send an e-mail as anyone in the world, even the President of the United States. There is no verification check.

We can tell that a header is spoofed by looking closely at the header information when the e-mail comes in, and what really counts is the underlying IP address it originated from. Of course, if you had their IP address, you could track them down in no time, so they also spoof that in a way: They relay mail through computers that are infected with viruses designed just to allow this relaying. These spammers find underground programs to scan for these open relays, or often they just pay the owner of a botnet.

So back to how and why you get the bounce messages: I know my acquaintance would just randomly pick roughly 40-50 unlucky e-mail addresses per spamming computer out of his list of millions, and put them in the "From" box of his spamming programs. So any time one of those e-mails gets sent to an undeliverable e-mail address, the bounce message goes right back to the unlucky e-mail address that was used in the forged header.

The only thing you could do is turn off or block all bounce messages, but this is something that is really done at the server level, a level most people do not have access to.

The good news is that they will probably randomly pick different e-mail addresses next time, so the problem will hopefully go away...for you.

For anyone trying to fight spammers, I do not think you can really fight them by trying to track them down using IP addresses, but one thing that struck me watching the operation I mentioned: Follow the money. That is how to really track someone.

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Thank you to the first +1 voter. I feel that this is one of my most interesting answers, and I wasn't even sure anyone read it because I got to the question a little later. –  KCotreau Jul 19 '11 at 6:56
    
@Randolf Richardson First, since I am pretty sure it was you, who put me over 10K, thank you. Not that I am looking for an upvote, I consider this one of my most interesting answers here. You might find it interesting since you are an anti-spam guy. That is if you are not the one, who was that first upvote. –  KCotreau Jul 19 '11 at 7:12
    
That's way more detail then I expected. Good answer for reference as well I believe :-). Although it does not "solve" the problem ;-). –  yankee Jul 19 '11 at 9:43
    
@yankee Thank you for marking it anyway. I realize that it does not solve it, but as a consultant, I have been in charge of e-mail systems that included: 52,000 users for a Fortune 50 company, a British conglomerate with more than 20 companies and another company with 1000 users (and many more smaller). Just three weeks ago, I installed e-mail servers remotely on two continents for a company. I am not trying to brag, but as you can see, e-mail is my specialty, so when I say that based on the way e-mail works, you can't stop it (unless the mail server blocks ALL undeliverables), you prob can't. –  KCotreau Jul 19 '11 at 11:33
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The fact that you don't mention anyone actually contacting you about spam from your address is the clue. What did the mails contain? An ad?

Chances are that those mails are not going to anyone with your return address but you. It is a common practice of spammers to simulate returned mail in order to get their wares through spam blockers. It is highly unlikely that anyone would have their own address blocked in their spam filter. But that is what I suggest that you do.

If anyone contacts you about spam coming from you, that may be another matter.

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I don't know what the mails contain. It's all Russian, I don't understand it... But many failure notices say that the mail was rejected because it is spam ;-). Anyway thanks for taking the time to answer :-). –  yankee Jul 19 '11 at 9:47
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