Dealing whith junk mail

Pablo Saratxaga (
Tue, 20 May 1997 18:24:32 +0200 (MET DST)


I apologize this message isn't really related whith ifmail, but as many
of you run internet-->FTN gateways that may interest you.

You have surely seen an allways increasing amount of bulk-email going to
fidonet or other FTN addresses, that hurt the FTN networks, due to the
nature of communications mainly phone-based.

However sendmail provides a powerfule yet not very known way to deal whith

In the /etc/ put :

# domain/address you want to filter

#sender-address $| recipient-address
# if you are the gateway yourself use this lines
R < $+ @ $=b > $| $* $#error $: Unknown user $3
R $+ @ $=b $| $* $#error $: Unknown user $3
R < $=b > $| $* $#error $: Unknown user $2
R $=b $| $* $#error $: Unknown user $2
# if you receive mail from FTN, use this, replace whith the
# correct address of the gate for you.
#R $+ % $=b @ $| $* $#error $: Unknown user $3
#R $=b @ $| $* $#error $: Unknown user $2
# the rest is ok.
R$* $@ OK

then in the /etc/sendmail.cb fiel you can put a list of domains and email
adresses you want to reject any mail from them. The reason of rejection
will show as "Unknown user recipient-address" so chances are that they will
think the adress invalid and drop from their lists.
If you receive the mail trough FTN the adresses in the sendmail.cb file
should be user%domain instead of user@domain, if you receive through both
FTN and smtp (like I do) just put the both forms and use the two sets
of lines in the file.

You can also taylor it to reject spams only when it is for adresses of the
fidonet domain, in case the achine where the gating is done is the property
of some entity that wouldn't allow rejection of mails for their domain,
just modify the lines like:

R < $+ @ $=b > $| $* fidonet $* $#error $: Unknown user $3fidonet$4


Here is an exemple of sendmail.cb I use :

Thanks again for reading, and sorry for this out-topic letter, but I think
that would gratly improve the quality of gateway traffic and of FTN networks
if those rules are correctly implemented.

Good luck !


A bientôt, Pablo Saratxaga

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