Spam from same email ID.

[Steve Freegard]

On 09/09/10 10:24, Glenn Steen wrote:
>>
>> You might have DKIM and SPF in SpamAssassin; but these are totally useless
>> unless the domain you are having this problem with (e.g. 123l.com) actually
>> publishes or uses them...
>>
>> smf at smf-laptop:~$ host -t TXT 123l.com
>> 123l.com has no TXT record
>>
>> Same with smf-spf or milter-spiff; they'll only fix this problem if a policy
>> is published for the domain in question (ideally a '-all' hard fail).
>>
>> Regards,
>> Steve.
> I'm a bit rusty on the rendmaul...Oops, sendmail ... side of things,
> but couldn't one do pretty much the same as I do in PF? That is, use
> an access-like map to disallow ones own (or customers) domain(s) as
> (envelope) senders? The loss for any typical smaller business would be
> greeting card stes etc, so shouldn't matter much.
> Sure, SPF with correct DNS record(s) would perhaps be easier, but ...
> sometimes it is easier to futz with ones MTA than with a (possibly
> externally managed) DNS:-).

No reason why you couldn't add something like:

from:mydomain.com         REJECT

But there be dragons here if you use the box for anything other than 
inbound mail e.g. SMTP AUTH, smart host or if you have a secondary MX. 
I've never tried it - but I suspect that you can mitigate some of that 
using 'connect:ip.ip.ip.ip    OK'.

Cheers,
Steve.