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Poco Forums • View topic - Mail without my address

Mail without my address

Discussion on Bayesian and standard junk mail filters

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Mail without my address

Postby FieldDir121 » Mon Nov 01, 2004 7:05 pm

On my business account I get e-mail with info@<company>, postmaster@<company> and sales@<company> that doesn't have my address anywhere in the header. If I send email to any of these accounts from my personal account I do not get a copy so it isn't a mail server problem. Somehow spammers are getting messages to me that do not have my address. How do they do this? How can I prevent it, other than described below?

I have sort of solved the problem by filtering for messages without my address in either TO: or CC:. I also sort all messages with sales, info, postmaster and webmaster whether my address is included or not. These are all deleted rather than placed in the junk mailbox. They are always spam.

Once these messages no longer make it to the Bayesian filters I found the word lists grew more slowly and were more accurate so I deleted the contents of the word lists and started over. So far no false positives and fewer false negatives. the junk list has 3,000 words instead of 50,000 as it had before.

Something else that was happening was that e-mails from senders in my address book were ending up in the spam mailbox. I thought e-mails from senders in the address book were exempt. Is that not the case?

I had to add my own filter that put messages from people in my address book into the appropriate mailbox and then stop processing. Should I have had to do that?

Jim
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Re: Mail without my address

Postby robin » Tue Nov 02, 2004 5:08 am

FieldDir121 wrote:On my business account I get e-mail with info@<company>, postmaster@<company> and sales@<company> that doesn't have my address anywhere in the header. If I send email to any of these accounts from my personal account I do not get a copy so it isn't a mail server problem. Somehow spammers are getting messages to me that do not have my address. How do they do this? How can I prevent it, other than described below?
This is what happens when you send a message BCC. You send it to your SMTP server along with a list of the BCC addresses, the server takes this message and the list of addresses and says to each of the respective recipient servers "Oi, I've a message for this address", to which it replies "Okey dokey..." That's how BCC works.

Not much that you can do about it though except, as you noted, filter on whether your address is in the To: or CC: fields.

My wife gets spam like this: it is addressed to another user at her ISP and BCCd to her (among others I suspect). I have a filter that checks for this name in the To: field and deletes the message if found (my wife doesn't know this other person and has no reason to get messages that are also addressed to her).

HTH
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Re: Mail without my address

Postby Pete » Tue Nov 02, 2004 2:11 pm

FieldDir121 wrote:I have sort of solved the problem by filtering for messages without my address in either TO: or CC:.

The only potential problem with this is that some people that you know and/or legitimate companies might use the BCC field (as Robin described) instead of the TO or CC. They would do this if they didn't have the technology or the desire to send a separate message to each recipient. They would use the BCC field so that you wouldn't have to look at a long list of recipients at the beginning of the message, and also to avoid revealing other recipients' email addresses. You wouldn't see such messages before your filter deleted them.


FieldDir121 wrote:I had to add my own filter that put messages from people in my address book into the appropriate mailbox and then stop processing. Should I have had to do that?

Yes. :)
However, you don't have to explicitly perform a "stop processing" action -- that happens automatically whenever you move or delete a message.
Pete
 

Postby Pete » Tue Nov 02, 2004 2:33 pm

Also, I personally would trust the Bayesian Filter to correctly identify these messages as spam rather than use my own filter. However, you might have to classify several of them as junk before the BF would consider it spam. It would be interesting to know if this would work and how many times someone would have to train the BF.
Pete
 

Postby Hogyt » Tue Nov 02, 2004 6:33 pm

Or you could take the SpamAssassin approach and add a small amount to the junk score (not enough to classify it as junk by itself) if your email address isn't in the headers. Combined with other rules, like adding to the score if the sender isn't in your address book, it may prove effective.
Mat
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Mail without my address

Postby FieldDir121 » Sun Nov 14, 2004 5:59 am

I found that mail with "info", "sales", "postmaster" or "webmaster" in "to" or "cc" that also came to me was always junk. I created a special mailbox called "crap" and had all such messages put in there for several days. 100% spam.

I now have the filter delete them. Messages to multiple people may be valid so I do not delete those. I am still undecided on messages without my name in "to" or "cc". Currently they are being deleted. I may create a special mailbox called "Not Me" and put them there.

I have also found that many messages with large numbers of random words just confuse the Bayesian filter. It is better to find a way to delete such messages, either manually or with filters, rather than adding the words to the junk list. Otherwise, eventually all words will end up on the junk list. That, I am told, is the goal of such messages.
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