This seems to have been a FAQ with the most common answer being "that's
a stupid thing to do."

At any rate, I think it's worthwhile for my domain, so this is what I
added to my sendmail.cf:

SLocal_check_mail
R$* $: $1 $| $&{client_addr}
R< $* @ $* highlandsun.com > $| 66.221.212.169 $@ <OK>
R< $* @ $* highlandsun.com > $| $* $#error $@ 5.5.4 $: "553 You
agree to pay me US$1000.00 for each use of my domain name, payable
monthly. Repeated use constitutes your acceptance of these terms."
R< $* @ localhost $* > $| 127.0.0.1 $@ <OK>
R< $* @ localhost $* > $| $* $#error $@ 5.5.4 $: "553 Real domain
name required for sender address"

Since all of my outbound email originates on this machine, anything
coming from elsewhere is clearly an abuse.

hyc a écrit :
> Since all of my outbound email originates on this machine, anything
> coming from elsewhere is clearly an abuse.

Then, you should also register a SPF entry (<http://www.openspf.org/>).

Xavier Roche wrote:
> hyc a écrit :
> > Since all of my outbound email originates on this machine, anything
> > coming from elsewhere is clearly an abuse.
>
> Then, you should also register a SPF entry (<http://www.openspf.org/>).

Of course. Did that, two years ago, as anyone can determine for
themselves:

> server ns.propagation.net
Default server: ns.propagation.net
Address: 216.221.160.10#53
> highlandsun.com
Server: ns.propagation.net
Address: 216.221.160.10#53

highlandsun.com text = "v=spf1 a mx:highlandsun.propagation.net"
highlandsun.com mail exchanger = 10 mail.highlandsun.com.
Name: highlandsun.com
Address: 66.221.212.169
highlandsun.com nameserver = ns.propagation.net.
highlandsun.com nameserver = ns2.propagation.net.
highlandsun.com nameserver = ns3.propagation.net.
highlandsun.com nameserver = ns4.propagation.net.
highlandsun.com nameserver = ns1.lax.propagation.net.
highlandsun.com nameserver = ns2.lax.propagation.net.
highlandsun.com
origin = ns.propagation.net
mail addr = hostmaster.propagation.net
serial = 20030634
refresh = 86400
retry = 7200
expire = 3600000
minimum = 28800

hyc wrote:
> SLocal_check_mail
> R$* $: $1 $| $&{client_addr}
> R< $* @ $* highlandsun.com > $| 66.221.212.169 $@ <OK>
> R< $* @ $* highlandsun.com > $| $* $#error $@ 5.5.4 $: "553 You
> agree to pay me US$1000.00 for each use of my domain name, payable
> monthly. Repeated use constitutes your acceptance of these terms."
> R< $* @ localhost $* > $| 127.0.0.1 $@ <OK>
> R< $* @ localhost $* > $| $* $#error $@ 5.5.4 $: "553 Real domain
> name required for sender address"

Btw, I think 550 / 5.7.1 is the more appropriate error code here.