[ale] Strange sendmail (and postfix) spam issue: accepting fail "from" myself?

Alex Carver agcarver+ale at acarver.net
Tue Mar 29 16:58:59 EDT 2016


On 2016-03-29 12:04, Derek Atkins wrote:
> Hi,
> 
> On Tue, March 29, 2016 2:30 pm, Alex Carver wrote:
>> I would first enable reverse DNS checks.  That would probably put an
>> instant stop to the practice because the IP and domain won't match.
>>
>> It will also stop mail coming in from hosts without reverse DNS but
>> that's an option to weigh (and maybe not the best choice if this is the
>> server I'm thinking it is).
> 
> Yeah, unfortunately I can't turn that on because of real v6 clients
> connecting.  I've turned it on before and been yelled at because it blocks
> too much.  :(
> 
>> Alternatively set up a rule that if the from domain matches yours, it
>> must also match your IP address.
> 
> This is something I'd love.  So, how do I so this in sendmail-speak?
> I've spent too much time googling and haven't found a macro that does it,
> and honestly these days my sendmail config fu is based on what's in the
> .m4 macro documentation.  :(

I wouldn't have expected v6 to matter.  It's just rDNS so if that's not
set up then that's the remote side's fault.

As for the rule, no clue how to write it in sendmail's m4 macros, I use
exim for the MTA.


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