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qmail Spam Issues

Posted on 2012-03-14
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Last Modified: 2012-06-25
Dear Experts,

We have installed qmail in our new server and started running our website in the server.
It was a dedicated server and did not have much experience in the mail server configuration. So we installed it in the default form.

Now my server people complain that we are sending spam with the server. We have also confirmed the somehow our mail server is used to send some spam emails.

Can anybody send the email using our qmail mail server FROM A DIFFERENT server?

Or will it be somebody hacked into our server and wrote a php program to send the emails?
I doubt the first one anyway?

If so, how can I prevent others to not use the mail server but just allow my own php files to send email with the mail server?
Can anybody please advice?

Thanks,
Jacob
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Question by:jacobbbc
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by:Duncan Roe
Duncan Roe earned 334 total points
ID: 37723894
I run qmail but only now as a vestigial service for pushing out aliased mail.
I suspect someone is using your server as an email relay. I've perused the man pages, but I don't see how they would do that. Possibly your locals are too open - worth checking.
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by:1ly4me
1ly4me earned 166 total points
ID: 37724115
Use nmap to check port number 25 (This is for SMTP - sending mails), If the port is open close it, and open relay only to localhost.
If your SMTP port open to all, any one can use it as a SMTP gateway and can send any kind of emails.
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by:
Duncan Roe earned 334 total points
ID: 37724461
lsof -i (run as root) should show port smtp listening on all interfaces for tcpserver run by qmaild. I don't think that means it can or will relay.
Make sure that RELAYCLIENT is not set in the environment of qmail-smtpd. You can do this from the proc file system.
Also if you think you are being used as a relay, check /var/log/qmail/current
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