[Workaround.org] Preventing backscatter with Postfix

Oliver Ladner workaround-ml at lugh.ch
Fri Jul 30 10:06:42 CEST 2010


Hello all,

Recently my mailserver got re-listed at backscatterer.org, an RBL run  
by the infamous UCEPROTECT guy(s).

I read http://www.postfix.org/LOCAL_RECIPIENT_README.html#change and  
so I added this to my main.cf:

local_recipient_maps = $virtual_mailbox_maps

So if I query this map with postmap -q i get "1" back if the user  
exists, but nothing if it's missing. At the end of that URL above is a  
notice:

"NOTE: a lookup table should always return a result when the address  
exists, and should always return "not found" when the address does not  
exist. In particular, a zero-length result does not count as a "not  
found" result."

Might this be the problem? I'd simply like to prevent spoofed DSNs. It  
doesn't seem to work like this.

I don't think amavis is the problem, my configuration is as follows:

# grep -r final_*_ /etc/amavis/
/etc/amavis/conf.d/50-user:$final_spam_destiny  = D_PASS;
/etc/amavis/conf.d/20-debian_defaults:$final_virus_destiny      =  
D_DISCARD;  # (data not lost, see virus quarantine)
/etc/amavis/conf.d/20-debian_defaults:$final_banned_destiny     =  
D_BOUNCE;   # D_REJECT when front-end MTA
/etc/amavis/conf.d/20-debian_defaults:$final_spam_destiny       = D_PASS;
/etc/amavis/conf.d/20-debian_defaults:$final_bad_header_destiny =  
D_PASS;     # False-positive prone (for spam)

Thanks in advance.

Oli


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