Block null "from" in logs

[Alex Neuman]

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Matt Hampton wrote:
>> Anyone can help me to make a rule to block e-mails that comes with 
>> null from
>> in header (from=<> in mail.log).
>>  
>>
>
> If you are running sendmail and don't mind running milters you can use 
> milter-regex
>
> http://www.benzedrine.cx/milter-regex.html
>
> Takes some playing around to get it to compile under Linux but it 
> works nicely.  I have a client that was getting thousands of DSNs to 
> his domain which were being sent to different users.  His domain only 
> has about 20 valid senders so this was all the result of spams.
> We have temporarily block all Null sender messages to his domain only 
> by using the following:
>
> reject "This domain does not accept DSN messages"
> envrcpt /@domain.co.uk/ei and envfrom /^$/
> envrcpt /@domain.co.uk/ei and envfrom /^<>$/
> envrcpt /@domain.co.uk/ei and envfrom /mailer-daemon@/ei
>
> I will re-iterate what everyone else has said about RFC's.  From 
> direct experience we also have had to change the way in which 
> mailfromd (a version of milter-sender) verifies addresses as sites 
> that block DSNs  were being blocked from sending to our clients.  We 
> use the address "addressverifier" rather than "<>" now and this 
> reduces the number of failures.
>
> matt
>
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I've also had to tweak milter-sender to use a valid address when 
verifying the sender, because a lot of ISP's in my country block from:<> 
messages.

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