While setting up and configuring a new Postfix mail server, I attempted to use the Webmin ‘Read User Mail’ module, and got this error.
Module Config Read User Mail
The mail server set in the module configuration was not found on your system, You will need to adjust the configuration to use the correct server.
Solution
At first I thought I needed to enter a servername into the config. However it seems when my VPS hosting company provisioned my server it installed sendmail by default, I needed to change it to Postfix instead.
1. Open the link it provides to the Read User Mail module configuration.
2. Scroll down to the system configuration section.
3. Change the Mail server Installed to Postfix.
4. DON’T FORGET to scroll to the bottom and press ‘Save’.
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After my recent DNS troubles, I was checking my mail server’s (MX) records, and got a warning about not having any reverse lookup records (PTR) configured properly. I telnetted to the mail server on port 25, and saw it was responding with the servers host-name.
I know my records are correct for the FQDN of the server, I just needed to change its welcome banner.
Solution
Change the Postfix Welcome Banner by Editing The Postfix main.cf File
1. Connect to the server via SSH, (or open a terminal session). Logon as, (or su to) root.
2. Execute the following command;
[box]
nano /etc/postfix/main.cf
[/box]
3. Locate and edit the myhostname value, to match your servers public FQDN.
4. Once you have saved and exited nano, restart the Postfix service with the following command;
[box]postfix stop && postfix start[/box]
Change the Postfix Welcome Banner Using Webmin
1. Connect to the Webmin console > Postfix Mail server > General Options.
4. Scroll down to internet host-name of this mail system > Edit to match your servers public FQDN > Save and Apply.
5. Stop then Start Postfix.
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I got a Tweet this morning, to say the site was down.
I checked and the VPS was off-line? So I powered it on and waited a few minutes. Linux is not one of my strongest technical areas so I did some Googling about what logs to check etc. When I looked in the var/log/messages log it was full of these, up to the point where it went down;
After some more reading it became clear that I’d been used in part of a DDOSDNS amplification attack. This was possible because the DNSBIND server that I was running had DNS recursion enabled. This means that if it can’t resolve a DNS query then it attempts to resolve the DNS query for you, (currently this is the default setting). You can check yours online with this tool, (you don’t want it to say ‘open’).
Solution
Disable BIND DNS Recursion (From the Console)
1. Log onto the server directly or via SSH, navigate to, and open the named.conf file.
[box]cd /etc
vi named.conf [/box]
2. Near the top of the file locate ‘recursion yes;‘
3. Press ‘I’ to go into ‘insert’ mode, using the arrow keys navigate to ‘yes’ and change it to ‘no’, Press {Esc} then to save and exit type ZZ (for some reason :wq wouldn’t save on mine!).
4. Then restart BINDDNS. Check once again with the tool and hopefully now it will say ‘no response’
[box] service named restart[/box]
Disable BIND DNS Recursion (From Webmin)
1. Log into Webmin > Servers > DNSBIND Server > Edit Config File.
2. Change ‘recursion yes;‘ to ‘recursion no;‘ > Save.
3. In the top right hand corner click ‘Stop BIND’ then ‘Start BIND’.
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I like to keep my CentOS server updated as much as I can, but the last couple of times I’ve gone to run the upgrade of the Webmin console, I’ve got this;
error: Failed dependencies:
perl(Net::SSLeay) is needed by webmin (version)
Solution
1. As error messages go this is not a bad one, it obviously needs perl installing. So SSH into the server and execute the following command;
