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

Les Mikesell les at futuresource.com
Mon Mar 12 12:32:30 EDT 2007

WBrown at e1b.org wrote:
> mimedefang-bounces at lists.roaringpenguin.com wrote on 03/11/2007 10:35:43 
> AM:
>> 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
> What are you currently doing with those external addresses?
>> 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?
> No.  You are perfectly free to respond with 550 unknown user to the "RCPT 
> TO: someone at external.com" command.  It is up to the sending SMTP host to 
> deliver the message to the right server for the recipient. The exception 
> would be for user where your server is the designated relay for their MUA. 
>  Access to that should be restricted by requiring authentication, or 
> restricting it to internal IP addresses.

Yes, the 5xx rejection should be happening already if the message comes 
from a network not specifically marked as RELY in your access file. 
Sendmail should only attempt to deliver to your own addresses from other 
sources.  Also note that the header contents aren't used by sendmail 
unless the message is passed on the command line with the -t option. 
Otherwise only the envelope addresses are used and they don't have to 
correspond with the visible headers.

   Les Mikesell
    les at futuresource.com

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