[Mimedefang] Hot do I stop becoming a spam relay.

Andrew Watkins andrew at dcs.bbk.ac.uk
Sun Mar 11 14:19:30 EDT 2007


Looking at the e-mail in a bit more detail, I may be wrong and it is not 
Bcc. For the last 24hours I have had about
1000 postmaster return messages and at first I thought we were the 
sender of the original spam e-mail, but after some
more checking I relise that it is just our domain being used as the 
sender address.
So, at least we are not be the sender, just the one being used as the 
 From header.

Going back to my original e-mail. I just checked. I logged onto 
gmail.com and did the following:
       From:     Me at gmail.com
       To:        NoSuchUser at yahoo.co.uk
       Bcc:      me at dcs.bbk.ac.uk (Work Address)

And I got the e-mail at my work address? So, Why did I get it?


>On 11 Mar 2007 at 14:35, Andrew Watkins wrote:
>>First of all my sendmail does not allow relaying, but I am now getting a 
>>lot of e-mail where email is sent to an unknown local user and then 
>>there is a BCC to some other location:
>>for example:
>>    From: spammer at domain.com
>>    TO:    XXX at ourlocal.domain.com
>>    Bcc:   someone at external.com
>>I guess the letter of the of the law I should deliver the e-mail, to the 
>>external address, since typo 's do happen, but there must be away round 
>>it. May be I could not deliver Bcc if the to address is invalid?
>First, if there is a "Bcc:" header in the incoming SMTP data, the  
>server at the other end screwed up...the whole point of "Bcc:" is that 
>other recipients aren't supposed to know about it.
>Second, sendmail doesn't deliver based on headers from SMTP data...it 
>delivers based on the "RCPT To:" command in the SMTP transaction.  So, 
>whatever might be in a "Bcc:" header isn't going to do anything.
>Now, if you have some program to deliver the e-mail locally that looks 
>at headers and creates a new e-mail message if there is a "Bcc:" 
>header, then that's the problem.
>"sendmail -t" is an example of a command that does this sort of header 
>parsing.  It's really only used for initiation of sending mail, and I 
>think it's ignored when in daemon mode, but check to see if you are 
>starting your daemon with this flag, just in case.

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