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Old 01-09-2011, 09:18 PM   #1
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Registered: Dec 2010
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Troubleshooting mail with CentOS/ Webmin: first steps?

Thought I'd cross-post this here, as well as on the Webmin forum (particularly seeing as this place is a little more livelier!).

I've got a troublesome Virtualmin/ Webmin installation that seems to have an endless queue of problems. My VPS provider has managed to get me to the point of having an operational Vmin/Wmin installation, but now I've run in to a problem with mail - when I send a test email to one of the default addresses for a virtual server (eg, I immediately receive a 'mail delivery failed' message, like this:

This message was created automatically by mail delivery software. A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed: postmaster@[] No Such User Here


What I'd like to know is, what steps can I take to troubleshoot this problem?

I know that I can ask my VPS provider to help, but I'd like to try to understand the problem, too, and learn from it.
Old 01-09-2011, 10:53 PM   #2
Registered: Mar 2006
Location: Singapore
Distribution: RHEL, CentOS
Posts: 132

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I assume you are trying to send email locally. All the mail services default is allow to send locally. In this case, you only need to create postmaster account.
If you are relay to another server, you need to make sure your destination mail server has postmaster account.
If you are hosting that '' at your server, you need to make sure all the full setup of mail service is take in place.

Old 01-09-2011, 10:55 PM   #3
never say never
Registered: Sep 2009
Location: Indiana, USA
Distribution: SLES, SLED, OpenSuse, CentOS, ubuntu 10.10, OpenBSD, FreeBSD
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Well, I don't generally work with the Webmin interface, but we are going to need a lot more information.

The error No Such User seems to explain it have you set up postmaster with a mail account?

Can you send mail to yourself from that server? (This will confirm the server is working)

Do the logs reveal anything? (/var/log/mail)

Have you already set up DNS records for the domain? (Specifically MX Records for Mail Delivery)

Do you have the firewall set to allow SMTP connections? (TCP Port 25)

You don't say what mail server your running, Postfix, Sendmail, QMail ... Which?

If your still having problem post back with the config files for the mail server and the pertinent parts of logs. Many here are willing to help, we just need more information.
Old 01-11-2011, 11:18 AM   #4
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Registered: Dec 2010
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Well, I also posted about the issue on WHT, so save me typing the background, I'll copy/paste it here:

Okay, so I've just set up Virtualmin and Webmin on my VPS (with a few tweaks from my VPS provider). I've tried sending a test email to the aliases that Vmin sets up, as well as an actual account. All I get back is an error saying that the address couldn't be found.

I sent a ticket to my VPS provider and he said that I need to set up an MX record to point to my VPS to receive mail (which I hadn't done because I thought I didn't need one, seeing as web, mail and DNS are all on the same server).

When I set up DNS with Webmin, I followed the guide here:

So, as I'd set up '' in Webmin/BIND as an A record and as a mail server record, I thought that would be sufficient.

Presumably, my VPS provider is suggesting that I set up '' as an MX record with my domain at my domain registrar's control panel (1&1)?

What I don't understand is why, when I was on a shared hosting account with another host, I could just register domains, point their nameservers to the ones my host supplied and then just host sites and mail for those domains without having to deal with MX records. What is different in this situation?
Old 01-11-2011, 11:15 PM   #5
Registered: Mar 2006
Location: Singapore
Distribution: RHEL, CentOS
Posts: 132

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Either you use your domain register DNS server or your own DNS server is same. You must create MX record for your mail server.
Because when you send email to other domains. Other mail servers will check your domain MX record, SPF record, reversed DNS record. If not found all these record, they will simply reject your email.
If I am not wrong, even your email service will check your own domain MX record before relay to other servers.



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