Posts Tagged ‘SPF’

How to disable spammer domain in QMAIL mail server with badmailto variable

Thursday, July 12th, 2012

I've recently noticed one of the qmail SMTP servers I adminster had plenty of logged spammer emails originating from yahoo.com.tw destined to reache some random looking like emails (probably unexisting) again to *@yahoo.com.tw

The spam that is tried by the spammer is probably a bounce spam, since it seems there is no web-form or anything wrong with the qmail server that might be causing the spam troubles.
As a result some of the emails from the well configured qmail (holding SPF checks), having a correct existing MX, PTR record and even having configured Domain Keys (DKIM) started being marked, whether emails are sent to *@yahoo.com legit emails.

To deal with the shits, since we don't have any Taiwanese (tw) clients, I dediced to completely prohibit any emails destined to be sent via the mail server to *@yahoo.com.tw. This is done via /var/qmail/control/badmailto qmail control variable;

Here is content of /var/qmail/control/badmailto after banning outgoing emails to yahoo.com.tw;;;

qmail:~# cat /var/qmail/control/badmailto
[!%#:\*\^]
[\(\)]
[\{\}]
@.*@
*@yahoo.com.tw

The first 4 lines are default rules, which are solving a lot of badmailto common sent emails. Thanks God after a qmail restart:

qmail:~# qmailct restart
....

Checking in /var/log/qmail-sent/current, there are no more outgoing *@yahoo.com.tw destined emails. Problem solved …

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Fix to mail forwarding error “Received-SPF: none (domain.com: domain at maildomain does not designate permitted sender hosts)

Tuesday, October 18th, 2011

I’m Configuring a new Exim server to relay / forward mail via a remote Qmail SMTP server
Even though I configured properly the exim to forward via my relaying mail server with host mail.domain.com, still the mail forwarding from the Exim -> Qmail failed to work out with an error:

Fix to mail forwarding error "Received-SPF: none (domain.com: domain at maildomain does not designate permitted sender hosts)

I pondered for a while on what might be causing this “mysterous” error just to realize I forgot to add the IP address of my Exim mail server in the Qmail relay server

To solve the error I had to add in /etc/tcp.smtp on my Qmail server a record for my Exim server IP address xx.xx.xx.xx, like so:

debian-server:~# echo 'xx.xx.xx.xx:allow,RELAYCLIENT="",QS_SPAMASSASSIN="0"' >> /etc/tcp.smtp

The QS_SPAMASSASSIN=”0″ as you might have guessed instructs Qmail not to check the received mails originating from IP xx.xx.xx.xx with spamassassin.

Finally on the Qmail server to load up the new tcp.smtp settings I had to rebuild /etc/tcp.smtp.cdb and restart qmail :

– reload qmail cdb

linux-server:/var/qmail# qmailctl cdb
Reloaded /etc/tcp.smtp.
- restart qmail

linux-server:/var/qmail# qmailctl restart
Restarting qmail:
* Stopping qmail-smtpdssl.
* Stopping qmail-smtpd.
* Sending qmail-send SIGTERM and restarting.
* Restarting qmail-smtpd.
* Restarting qmail-smtpdssl.

This solved the issue and now mails are forwarded without problems via the Qmail SMTPD.

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