Reject message only if it's not a spam

Antony Stone Antony.Stone at
Wed Sep 30 11:09:20 UTC 2015

On Wednesday 30 September 2015 at 12:47:41, Mateusz Krawczyk wrote:

> Antony,
> Thank you for your prompt answer.
> I would like to inform sender that sending message to some combination
> of recipients is not possible.

Okay - sounds a bit strange to me, but anyway...

> Until now we were using custom milter scripts in postfix and I would like to
> migrate it in to the MailScanner environment.

Sounds fair enough.

> I don't want to send reject messages to fake/spam recipients.I think
> that at the level of "reject message" it should be possible to send
> reject answer message only to messages which are believed not to be a
> spam.

Agreed - you don't want to send backscatter to faked senders.

I assume you're already using DKIM / SPF etc as far as possible, to verify the 

However, are you really seeing spam being sent to the "combinations of 
recipients which are not possible"?

I would have expected the spam you receive to be addressed to either:

 - single recipients, in which case the combination effect does not apply and 
there's no bounce / notify to be sent

 - (very) large numbers of recipients within your domain/s, which I suspect 
would not match your "impossible combinations" (or is this a miscalculation on 
my part?)

 - large numbers of recipients at both your and other domains (which of course 
you can only see from the From: header, not from the SMTP envelope), which are 
also not going to match your "impossible combinations" (or does this checking 
process include external domains in some way?)

Basically what I'm saying is that I can't see a use case where you get spam 
which should trip your bounce criteria, therefore sending the notification in 
cases where the combination of recipients is invalid should always be safe?

Maybe if we understood a bit more about the criteria you use for deciding to 
send a bounce / notify, that might help.



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