force SMTP authentication

[Brugnara]

It is possible to force SMTP auth. ?

We use different connection for public servers (MX record) on different IP and We use dedicated ports of Plesk-Qmail for our Client SMTP Relay server.

But for a Spammer is possible to connect and sent SPAM to local domains.

With a forced authentication this problem will to resolve.

Is there a method?

best regards
Brugnara

 

[atomicturtle]

You would quite thouroughly break incoming mail to your system if you did that

 

[Brugnara]

No, if you use different ports of incoming call and the filter control the incoming port (TCPLOCALPORT).

For example:
# File /etc/services
smtp25025 25025/tcp mail

# File /etc/inetd.conf
smtp25025 stream tcp nowait.1000 root /var/qmail/bin/tcp-env tcp-env -Rt0 /usr/sbin/rblsmtpd -b -r sbl-xbl.spamhaus.org -r your.rbl /var/qmail/bin/relaylock /var/qmail/bin/qmail-smtpd /var/qmail/bin/smtp_auth /var/qmail/bin/true /var/qmail/bin/cmd5checkpw /var/qmail/bin/true

Plesk qmail implements qmail-spp (http://qmail-spp.sourceforge.net/doc/) and I was experiment the plugin authrequired pathed with control of env TCPLOCALPORT, but environment variable SMTPAUTHUSER is non every time filled, because the program /var/qmail/bin/relaylock, I think, it use a database of client's IP and authentication is performed only once in a range of some connection period.

best regards
Brugnara