Qmail paranoid (reverse DNS)

[Orange_XL]

I recently turned on the paranoid option in tcpserver like this:

tcpserver -u 89 -g 89 -p -x /usr/local/vpopmail/etc/tcp.smtp.cdb 0 smtp /usr/local/bin/rblsmtpd -rbl.spamcop.net -rsbl.spamhaus.org /var/qmail/bin/qmail-smtpd &

The question is, am I blocking legitimate email? Spam has been reduced by 50%, but I also got 1 email from someone who had been blocked by mistake.

Anyone got any experiences with reverse DNS-lookups on mailservers?

[eaden]

basicly - yes you will block legitamate email.. and quite a lot of it, many many email servers don't have propery configured reverse dns.

You could try using a realtime blocklist of ip's that are known to spam, that way you will get a lot less "false positivies", or my favorite, spamassassin which flags email as spam, which lets you either still download it and put it in a "spam" folder, or delete it completely.

[Orange_XL]

Thanks. I am using several blocklist (spamcop, spamhaus) already.

I've been thinking about SpamAssasin, but I heard it uses quite a lot of resources?

[rayvd]

SpamAssassin has been really a godsend for me. Best way to run it if you're concerned about resources is to fireup the spamd (daemon) and then make calls to it using the spamc C-client instead of the Perl script. Much less overhead, and you can then have a centralized server that several mail servers could use.

Remember though, you have to restart the spamd server (SIGHUP seems to do nothing) to refresh any changes in your configuration file.

[daisho]

I use SpamAssassin with great success. Personally I do not like RTBL's. It seems that most of the people that run them are zelots and seem to be *VERY* slow at removing servers once fixed.

I would also not do reverse lookups on the mail server since for example in my situation QMail binds to the main IP address of the interface. Unfortunatly my SMTP IP is on an alias. Both addresses reverse but when you recieve mail from my server the IPs don't match.

There is a match for QMail but it doesn't seem to apply properly to 1.03. I'm looking for another patch that will from a source I trust.

Anyway just my 2 cents. I agree with rayvd comments about SpamAssassin. Really that's all you should need.

As a side note it lets each user change his/her settings or even turn it off.

Serge.