OT: how to block emails sent to too many recipients

Stephen Swaney steve at fsl.com
Mon Dec 20 14:26:41 GMT 2010

On Dec 20, 2010, at 9:00 AM, Denis Beauchemin wrote:

> Hello all,
> Someone seems to have found a way to use one of our MS servers to send spam. Each spam is sent to more than 199 recipients and the envelope from is never from our domain.
> I would like to block them but I am not sure how… I didn’t find anything in sendmail (except milter-limit which denies emails I have to deliver). I am now looking to SA.
> Does anyone know how to get the nrcpts= value found on the from= sendmail log line?
> Thanks!
> Denis
> PS: the spam is sent through our webmail (Horde). I cannot stop delivering emails from those servers.


Look at http://www.sendmail.org/m4/tweaking_config.html.

I think what you are looking for is confMAX_RCPTS_PER_MESSAGE. 

If confMAX_RCPTS_PER_MESSAGE is set, it will allow no more than the specified number of recipients in an SMTP envelope. Further recipients receive a 452 error code (i.e., they are deferred for the next delivery attempt).

But this blocks email to only the recipients that are over the limit.

Anthony Howe's milter-limit is really what you want. It has a lot more flexibllity and controls. I believe it's a free download from www.snertsoft.com.

Best regards,

Steve Swaney
steve at fsl.com
The most accurate and cost effective anti-spam solutions available

> Denis Beauchemin, analyste
> Université de Sherbrooke, S.T.I.
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