I recommend that you create a Sender Policy Framework (SPF) record for your domain. An SPF record is a type of Domain Name Service (DNS) record that identifies which mail servers are permitted to send email on behalf of your domain.

The purpose of an SPF record is to prevent spammers from sending messages with forged From addresses at your domain. Recipients can refer to the SPF record to determine whether a message purporting to be from your domain comes from an authorized mail server.

You can also lookup and test your SPF settings here.

So how do you add a SPF record to your domain. Well that is easy. A SPF record is nothing more than a TXT record in your DNS administration.

For a mail server the following DNS entries are defined:

As you can see there is a SPF record on the subdomain mail. A mail server that is receiving email from your domain retrieves the SPF record for your domain and verifies that the sending IP is auhtorized (by the SPF record) for this action.

The headers below of an email message show a domain without a SPF record:

x-store-info:w5JOV+GpEg16Hd3Liu8PdV6w7ot2s5vN
Authentication-Results: hotmail.com; spf=none (sender IP is 149.210.153.91) smtp.mailfrom=pkn-bnn-iw@mail.bjdejong.nl; dkim=none header.d=example.nl; x-hmca=none header.id=example@example.nl
X-SID-PRA: example@example.nl
X-AUTH-Result: NONE
X-SID-Result: NONE
X-Message-Status: n:n
X-Message-Delivery: Vj0xLjE7dXM9MDtsPTA7YT0xO0Q9MjtHRD0xO1NDTD0z
X-Message-Info: /3z5fcrqMMUC9h0cjR+uvxBFbZLKdSdtWqbr6MInznDp3iFPY3dfZtYCX/McjjMtj/elcEu8E8GWPTQfME0U8yM95EcDOlBGfpGY3FVu+zhLC/YR0apj5gaojeU+XWKSFMn5xpzk3h7mi1Zrgx5MoCPw09osDoKH5afXmmKDtnxMmXlqQKv2juplilatuJpfG2/eYbQkFt2x+JC9NXiXJelaZ42f/aaw0S73pWX0oijyKeKhtLa1cA==
Received: from mail.bjdejong.nl ([149.210.153.91]) by COL004-MC4F4.hotmail.com with Microsoft SMTPSVC(7.5.7601.23143);
	 Fri, 11 Dec 2015 03:05:49 -0800
Received: by mail.bjdejong.nl (Postfix, from userid 1053)
	id 2D6A93C2F6B; Fri, 11 Dec 2015 12:05:40 +0100 (CET)
To: berendjdejong@gmail.com, berendjdejong@hotmail.com
Subject: Your subject goes here
X-PHP-Originating-Script: 1053:class-phpmailer.php
Date: Fri, 11 Dec 2015 11:05:40 +0000
From: example <example@example.nl>
Message-ID: <421364d92aacfc35ba32861d8d20d90a@pkn-bnn-iw.nl>
X-Priority: 3
X-Mailer: PHPMailer 5.2.10 (https://github.com/PHPMailer/PHPMailer/)
Reply-To: <example@example.nl>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Return-Path: pkn-bnn-iw@mail.bjdejong.nl
X-OriginalArrivalTime: 11 Dec 2015 11:05:49.0453 (UTC) FILETIME=[E48E43D0:01D13403]

Message contents

As you can see there is no SPF record defined. You can verify this with the host command:

host -t txt mail.bjdejong.nl

Now after adding an SPF record to the domain and sending a new message (wait a while for the changes to take effect in the global DNS systems) headers are as shown below (send to a hotmail account):

x-store-info:w5JOV+GpEg16Hd3Liu8PdV6w7ot2s5vN
Authentication-Results: hotmail.com; spf=pass (sender IP is 149.210.153.91) smtp.mailfrom=example@mail.bjdejong.nl; dkim=none header.d=example.nl; x-hmca=none header.id=example@example.nl
X-SID-PRA: example@example.nl
X-AUTH-Result: NONE
X-SID-Result: NONE
X-Message-Status: n:n
X-Message-Delivery: Vj0xLjE7dXM9MDtsPTA7YT0xO0Q9MjtHRD0xO1NDTD0z
X-Message-Info: /3z5fcrqMMUC9h0cjR+uvxBFbZLKdSdtWqbr6MInznDp3iFPY3dfZtYCX/McjjMtj/elcEu8E8GWPTQfME0U8yM95EcDOlBGfpGY3FVu+zhLC/YR0apj5gaojeU+XWKSFMn5xpzk3h7mi1Zrgx5MoCPw09osDoKH5afXmmKDtnxMmXlqQKv2juplilatuJpfG2/eYbQkFt2x+JC9NXiXJelaZ42f/aaw0S73pWX0oijyKeKhtLa1cA==
Received: from mail.bjdejong.nl ([149.210.153.91]) by COL004-MC4F4.hotmail.com with Microsoft SMTPSVC(7.5.7601.23143);
	 Fri, 11 Dec 2015 03:05:49 -0800
Received: by mail.bjdejong.nl (Postfix, from userid 1053)
	id 2D6A93C2F6B; Fri, 11 Dec 2015 12:05:40 +0100 (CET)
To: berendjdejong@gmail.com, berendjdejong@hotmail.com
Subject: Your subject goes here
X-PHP-Originating-Script: 1053:class-phpmailer.php
Date: Fri, 11 Dec 2015 11:05:40 +0000
From: example <example@example.nl>
Message-ID: <421364d92aacfc35ba32861d8d20d90a@pkn-bnn-iw.nl>
X-Priority: 3
X-Mailer: PHPMailer 5.2.10 (https://github.com/PHPMailer/PHPMailer/)
Reply-To: <example@example.nl>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Return-Path: example@mail.bjdejong.nl
X-OriginalArrivalTime: 11 Dec 2015 11:05:49.0453 (UTC) FILETIME=[E48E43D0:01D13403]

Message contents

The SPF check is now passed. Also the output of the host -t txt mail.bjdejong.nl command  should now give you the TXT SPF record.

Also be sure to edit your /etc/mailname  to reflect the name of your server on an Ubuntu distribution.

Imagine the scenario in which you want to ssh backup your (VirtualMin) server to another (VirtualMin) server. This post describes in detail the steps to take.

First create your backup user on the server where you want to store the backup; lets name it remotebackup for example:

adduser remotebackup

Give a strong password to this user (although we will be using public / private  key authentication).

Then move to the server that creates the backups and create a RSA private / public key pair for the root user:

sudo ssh-keygen

Do not specify a passphrase (as the backup will run without user intervention). Leave the default filename for private and public key (id_rsa  and id_rsa.pub).

Now copy the public key (contents of id_rsa.pub) id to the user on the server where the backups have to be stored:

ssh-copy-id remotebackup@yourserver.net

If the copy fails because public key authentication is required over ssh you have to disable this first. To do this edit your /etc/ssh/sshd_config file and set the value for passwordauthentication to yes. Now execute the ssh-copy-id again and reset the value for passwordauthentication.

After the ssh-copy-id  has succeeded a new directory and file is created on the backup server. The directory is in the home folder of the remotebackup user and is called .ssh . In this directory a file is created, authorized_keys , which contains the public key from the root user of the server that wants to store the backups on this server.

To make things more secure it is advisable to make use of the rssh  shell for the remotebackup user. The rssh  shell is a restricted ssh shell. Only the commands that you specify are allowed in a rssh shell. To install it execute the following command on the backup server:

sudo apt-get install rssh

After rssh is installed successfully edit the file /etc/rssh.config . Uncomment the line containing the text allowscp  (VirtualMin executes backups with the scp  command).

Now edit the password file stored at /etc/passwd . Search for the line containing your backup user (remotebackup) at the start of the line and change the shell to /usr/bin/rssh.

Now if you try to login interactively over ssh you get a message saying that it is not allowed:

This account is restricted by rssh.

Allowed commands: scp

If you believe this is in error, please contact your system administrator.

Connection to bjdejong.nl closed.

Okay; this is good; VirtualMin only executes scp commands over your ssh connection.

Now goto your VirtualMin interface on the server that creates the backups and add the required backup schedules.

Create a full backup that runs every first of the month and create an incremental backup that runs every day.

Settings for the full backup. Mind the File on server setting which stores the files in a subfolder full .

The incremental backup uses the same settings except for the Backup level which you have to set to, guess what, Incremental.

There is one extra consideration if you create a backup user like this and that is User Disk Quota. When a user is created in a VirtualMin installation with quotas enabled the default maximum quota is 2Gb. That probably is not enough for your backup user. To change this goto your VirtualMin interface and adjust the quota:

VirtualMin -> System -> Disk Quotas; select Groups and select your backupuser.

Because VirtualMin cannot delete backups on the remote machine in this setup (only scp command is allowed for the remotebackup user) you can make use of the crontab to cleanup old backups. First create a script called cleanup.sh in your remotebackup home folder, place the following contents in it:

#!/bin/bash
# Script is executed via the crontab. All files older than 1 year
# are removed from the backup folder
find /var/backups/vps -mtime +365 -exec rm {} \;

Next edit the crontab for the remotebackup user and execute this script, lets say, every day at 0300:

sudo crontab -u remotebackup -e

Add this line to the crontab of the user and save it:

MAILTO="yourmail@yourserver.net"
0 3 * * * /home/remotebackup/cleanup.sh

Thats all there is to it. Your backups are save now!

Logwatch is an application that helps with simple log management by daily analysing and reporting a short digest from activities taking place on your machine. In this post a short manual for installing logwatch on your ubuntu box.

Install logwatch

sudo apt-get install logwatch

Configure logwatch

Edit the configuration file to suit your needs. Especially have a look at the “MailTo”, “MailFrom” and “Detail”.

/usr/share/logwatch/default.conf/logwatch.conf

After logwatch processes the file above at default.conf the file /usr/share/logwatch/dist.conf/logwatch.conf  is being processed. Settings in here will override the settings in default.conf! You most likely want to comment out the line that reads

MailFrom = root

After installation an entry is added to /etc/crond.daily/00logwatch

To execute logwatch from the commandline execute:

/usr/sbin/logwatch --output mail

Mail from logwatch not reaching you? Check your spam folder 🙂