Linux Postfix Mail Server Install and Configure: Quick Guide

Hello and welcome to our mini-tutorial on the configuration of the Linux Postfix mail server. No matter if you are a beginner or an advanced user this guide explores all the necessary steps that are needed to install, set up and maintain the secure email service using Postfix on Linux. Following this guide, you will not have issues when configuring your mail server thus guaranteeing seamless email delivery.

Key Takeaways:

• Applying for a Capstone or Thesis is a great opportunity to enhance your degree page 4
• Find out the processes involved in the configuration of the Linux based Postfix mail server
• Install and Set up a Postfix server on your Linux system
• Know the basic parameters and the configuration files of Postfix.
• Post Fix Set-up page 15 Certification Router page 18
• Test Postfix Page 14 Configuration Backup Supervisor: Harvey CaBlake Andres Bank Writer: Roger Alice Flap Publication date: May 8, 2014

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Introduction to Linux Postfix Mail Server

This subpart shows the introduction of a Linux Postfix mail server. Further on the authors will explain what is Postfix and the role of Postfix as mail transfer agent MTA within the scope of this paper. Moreover, authors will elaborate on how Postfix and MTA are explicated through the use of Simple Mail Transfer Protocol (SMTP). Everything that has been highlighted will be useful on the knowledge about how a basic functioning Postfix server works and why it is vital in the configuration of the email servers. Now that we have understood the needed information, further in this paper the rest of the configuration process will be explained in detail.

The Requirements Before Installing Postfix in Linux

However, there are several requirements that should be satisfied prior to proceeding with the installation of Postfix on your Linux system. In this section you will be provided guidance on what needs to be done in order to ensure proper configurations are made or other issues are eliminated.

Installations Already Made

The first thing to do is assess whether there have been any installations of Postfix or any other mail servers on your Linux system. This assists in eliminating conflicts and makes way for a clean installation of Postfix. To do so, open a terminal and type in the commands as follows:

Postfix Installation

In case any existing installations are found, it would be advisable to uninstall or remove these installations prior to starting the Postfix configurational processes.

Postfix Installation On Linux Systems

It is good practice to prepare any operating system installed on a machine by applying any available updates and installing any needed components prior to installing any software, including Postfix. In this regard, kindly carry out the following process.

For a Linux Machine It Is Important to Log Into the System and Update All The Packages So That The Postfix Can Be Installed< The packages required for Postfix to work properly need to be installed by executing the command outlined below. Make sure your system is up-to-date first.

sudo apt-get install postfix # command line package Secondly, The Necessary packages For The Configuration And The Ports Required To Be Opened Have To Be Configured. Make, Refer to your firewall documentation for specific steps to create firewall rules to allow traffic through the required Postfix ports/internal and outgoing traffic, if a firewall is activated on this Linux system.

By completing these prerequisites, you will have a well-prepared Linux system ready for the smooth installation and setup of Postfix.

In this section, we will write down a brief guide for the installation of Postfix on RPM Linux based distributions utilizing the Yum package manager. These are the steps to follow to have Postfix running on your Linux system within a few minutes utilizng the Yum Package Manager.

Utilizing Yum to Add Postfix

The beginning stage of installing Postfix is by executing the Yum package manager to first download and install the appropriate packages. Meny Yums is automatic and much more convenient as it allows the dependencies to be resolved automatically on your behalf.

Sudo yum install postfix

Before the mplication takes place this command will request that you provide your signature. Type Y and hit enter to commence the installation process. Yum then commences the integration process for the applicable packages and integrates Postfix on the device.

Beginning and Authorizing the Postfix Service

As soon as Postfix is fully integrated, the next step is to start and authorize the Postfix service. This will set Postfix to launch each time the system boots on, hence making your mail server available any time.

Sudo systemctl start postfix

Sudo systemctl enable postfix

The first of these two commands will activate Postfix’s service. The second will disable automatic turn of on the sequence of system start. Hence by using these two commands, Postfix will be active, geared to receive and send emails on the Linux device.

Setting Up Postfix Server Basic Options

The next task after Postfix is installed becomes the setup of primary parameters for postfix server. It is time to explore the configuration files, and how the different options can be adapted to meet your needs. Areas such as hostname and domain, mail spool directory, and a list of external SMTP servers are the areas that we will deal with also.

 

Postfix Configuration Files Analysis

As postfix is a mail server that’s has a number of configurable options, it comes with a number of configuration files that set it s operating principles and settings. As such, we shall explain two special files that are important in configuring Postfix, main.cf and master.cf in detail. With the knowledge of these files, you will be able to make changes to suit the required specifications of your Postfix mail server to your specifications.

First Configuration - main.cf

The primary file required to give Postfix configuration commands is always maintned in the directory of /etc/postfix/ and as such applies to many other files too. Within this file, the options for postfix can be both numerous or very few. Important areas such as policy regarding transport of email, managing spam, as basic details including the server name, would fit in this category as well.

The main.cf has several key settings that can be defined in it and they include;

myhostname: Specifies the fully qualified domain name (FQDN) of the computer that provides smtp services.

mydomain: Defines the domain name associated with the mail server.

mydestination: Expands the domains to which the mail server is responsible for.

mynetworks: Defines the range of networks or IPs that are allowed to send some mails via the server.

relay_domains: It indicates the domains against which the server has been configured as a relay.

smtpd_recipient_restrictions: It describes the policies regarding who can receive emails through the server.

Main.cf is one of the important files for the postfix configuration since it contains all the configurations related to emails and domains that the user handles. The configurations detailed here are the ones that influence how postfix is implemented so as to send and receive mails from defined domains.

The Purpose of master.cf in Postfix

Master.cf file location is in the same directory such as the main configuration file in postfix which is /etc/postfix/. The difference is that the two which are; the main.cf file from the master.cf file which all pertains to the basic settings in the mail server.

You can find entries within the master.cf file such as an SMTP server entry, a delivery agent entry, an entry for a virtual mail hosting service and so on. Each service has different settings that determines its behavior and interaction with other components of Postfix.

While analyzing the structure and purpose of the master.cf file, it becomes easier to configure the functionality of the postfix mail server so that it meets the exact needs of the user.

By modifying the master.cf file you can: - Enable or disable specific services. - Define ports, IPs and resource limits for lte service - Create and define new delivery agents or filters - Add advanced features like content filtering or virus scanning or encryption

Now let us take a look at the most common settings used in the main.cf configuration file:

• Mail server FQDN is defined in the configuration parameter ‘myhostname’. -
• The name of the domain under which the mail server will be used is defined under the parameter ‘mydomain’.
• All the servers that fall under the administration of the mail server are mentioned in the ‘mydestination’ section.
• Networks or IPs that are allowed to use the server to send relayed emails are mentioned in the ‘mynetworks’ section.
• In the section ‘relay_domains,’ the domains that will be relayed by your server are defined.
• In the elements ‘smtpd_recipient_restrictions’ rules are defined on who can receive emails through the server.

 

Testing Postfix (Part 1) - Use of Telnet

Once you have configured them all, you should deploy the Postfix server, but before that, it is crucial to check whether the server is fully functional. The correct way to do this is to send and receive emails by using a telnet command line.

Please follow these instructions to accomplish such testing of your Postfix configuration using telnet:

- Open the Windows command prompt or terminal window.

- Use the following command to connect to your Postfix server:

telnet :25

In this sentence, replace by the actual IP address of your server.

- You should see a response like:

Trying …

Connected to .

Escape character is '^]'.

- Let’s begin by the following command, which sets up the email conversation.

ehlo

In place of example.com, type your domain name.

- You should receive a response from the SMTP server stating the features it supports.

- Then, send an addressee:

mail from:

Replacing the first with ’your address’ email address.

- The server should then respond back that the email address has been accepted.

The command below allows the designation of the recipient:

Send your emails as follows rcpt to: [recipient’s email address]

For example, rcpt to: [recipient's email address] will be substituted with the actual recipient's email address in real life.

You should get a reply confirming that the recipient address has been accepted.

To begin, type the following:

data

After initiating a preceding command, now it is time to initiate the cover letter. Do not forget to press Enter after typing each line. Also, remember to place a single period (.) on a line of its own to capture the end of the letter.

To contact the recipient, type the following:

.

You were supposed to be shown a message confirming that the fax was posted sooner in the delivery operations.

You now have the option to conclude your session with the server by typing:

quit

Verification of emails and message reading log

When one is done with testing how the email’s transmission works, it is quite necessary to check whether the mail dispatch service is working correctly. This can easily be done by sending an email towards your personal address and looking through the mail logs for any mistakes that would take place.

To complete this aim follow the next steps that are provided below and read through the mail logs:

Email at least one test message towards one actual person in the real world.

Confirm successful mail delivery for the test email by checking the mail logs. The rest may differ on where the mail logs are kept, but the most common are likely these Depending on your Linux distribution, the mail logs can be found in the following locations:

Linux Distribution Mail Log Location

Ubuntu /var/log/mail.log

CentOS /var/log/maillog

Red Hat /var/log/maillog

Debian /var/log/mail.log

Access the mail log with a text editor or the command line.

Look for the respective entries that were recorded against the test email.

Look for errors or problems as referenced in the logs.

If there are no errors, it means the mail was correctly delivered.

These steps allow the verification if the Postfix configuration is okay and the mail is being delivered accordingly. It will also assist you to rectify issues prior to the deployment of the Postfix server.

Securing your Postfix mail server post

There is no doubt that security is one major issue while dealing with the Postfix mail server. In this section, we will look at ways that will help harden your server and your email communications.

Using TLS for Secure Email Conduction

It is important to install Transport Layer Security (TLS) on your Postfix mail server that ensures safe and secure transmission of your emails. TLS helps secure the connection between the mail servers which ensures the sensitive information remains private. Eavesdropping is thwarted, and your emails are sent securely over the Internet thanks to TLS’s protection of your emails as well.

Managing SSL OpenSSL Certificates

Used to encrypt that your Postfix mail server is always secure, SSL certificates are an integral of tremendous importance. It also helps ensure secure communication from your server to the email clients and guarantees that your server is real and intact. Managing SSL Certificates however is not a hard task because Open SSL is often used to do so. In this portion, we will provide information and guide you on how to obtain and manage SSL certificates with Open SSL focusing on the protection and reliability of your server.

Setting Up Relay or SMTP Providers for Emails

There may be cases where you are required to assist to configure Postfix with external SMTP providers or use it as a relay to send emails. This portion will provide a guide on how to configure your Postfix server to work well with external SMTP providers and also manage email relay to guarantee seamless sending and receiving of emails.

Using external SMTP providers allows you to boost your email communication strategies. Integrating Postfix with external SMTP providers allows you to profit from the provider’s robustness with respect to email delivery, effectively suppressing the chances of your email message being marked as spam.

Setting up Postfix to act as an email relay requires an outline installation that integrates with the organizational email relay servers. In this file, external SMTP server addresses and authentication parameters as they are required can be defined. Postfix would be able to relay emails that your organization intends to send by including a few particulars and credentials – and this is done via an external SMTP provider of choice.

Moreover, email relay can be done for the already identified purposes like transactional purposes or for notifications purposes for your application or website. This flagship feature allows you to ensure that important emails, such as notification emails, aid the customers more than make their lives harder.

Essentially, with the configuration done to the main.cf configuration file, save the file and restart the service such that Postfix comes into effect with the requisite modifications.

Setting up an email relay is important, since it allows the Postfix mail server to interact with various networks. This got me thinking about how important it is for you to use proper SMTP outfits as it will not only guarantee the delivery of your various emails, but also maintain the credibility of your email account.

How to Simplify SASL to Secure Posts

As SMTP Authentication maintains the authenticity of sending and receiving emails, it is of paramount importance. In this particular section we will demonstrate how to use SASL in postfix for forwarding emails. Following these procedures will make it straightforward to send emails, without the risk of disclosing other sensitive information.

Installing SASL’s pre-requisite Packages

In order for the SASL to work properly in relaying emails, it is pertinent to install the correct SASL packages for the specific distribution of Postfix you are using. Such Packages are needed for the development of libraries and any Authentication Mechanisms that may be required.

For Debian users like myself, the following procedure is useful when installing SASL images:

Turn on your Linux machine and open the console.

To install SASL packages on your distribution, use the command:

[sudo] apt-get install libsasl2-modules

Once the SASL packages have been installed successfully on your computer, you will be able to configure SMTP in Postfix with the required specifications.

Setting Up SASL Password Maps and Permissions

The subsequent task after the installation of SASL packages is the setting up of SASL password maps and permissions in Postfix. This setup facilitates the Postfix in validation of the authentication credentials which are submitted by the clients.

In this section, guides for setting SASL password maps and permissions are presented.

Start a text editor and open the main configuration file of Postfix, /etc/postfix/main.cf.

Find the parameter smtpd_sasl_auth_enable, and set it to yes to allow SASL authentication.

Include a password map file for SASL by adding this line to the configuration file:

smtpd_sasl_password_maps = hash:/etc/postfix/sasl_passwd

Important: It is not mandatory that you have to keep the password map file at this specific location and this specific name.

Use a text editor to create the SASL password map file in this case /etc/postfix/sasl_passwd. The file should include a definition of the username and password for each of the clients as follows:

example.com username:password

Important: In the example given above example.com is to be replaced with your domain name and username:password with the login credentials.

In order to enhance security, it is critical to limit outside access to the SASL password map file. This can be done by adjusting the permissions therewith using the command:

sudo chmod 600 /etc/postfix/sasl_passwd

Next, I will have to restart the postfix service so all the changes applied will be implemented effectively where I will use the command:

sudo systemctl restart postfix

You are now in control of the Postfix server which has been set up to make use of SASL for SMTP authentication. This will secure all your email exchanges with the additional authentication feature.

How To Set Up Email Forwarding With Postfix

In the context of email services, email forwarding is often required to send the incoming email to another outgoing one that is set to receive it. For example, forwarding an email Eugene sent to admin@random.online to nagee@hupcc.com. Forwarding an email through Postfix is very easy as you can do this through the configuration file. To avoid any form of limitations or restrictions that are imposed by specific email providers, you can set up your Postfix server to utilize email forwarding using the following steps:

Open up the appropriate configuration file within your preferred text editor. The configuration file is most likely to be found at /etc/postfix/main.cf.

The virtual_alias_maps parameter should be located within the configuration file. This parameter is used to define the location that contains the forwarding addresses including the databases.

Alter or add virtual_alias_maps parameter to the file or database which should be included. For instance, if the mappings are contained or located in /etc/postfix/virtual, use hash:/etc/postfix/virtual.

Prepare the forwarding records in the given file or database. For instance, if you wish to forward all john@example.com emails to jane@example.com, you would add a line like this: john@example.com jane@example.com. Every mapping has to be created on separate lines with the format source@example.com destination@example.com.

Once done, store the configuration file and close the text editor ‘nano’ or ‘vi’ as the case may be.

Restart the service for the changes to take effect. Re starting the postfix mail service will be slightly different for each Linux, for Ubuntu the command is “sudo service postfix restart”.

There you go your postfix server is now ready to map the incoming email accounts based on the parameters selected in the above file. Just to confirm it is working as expected test out the email forwarding functionality, you should be able to send email from your configured account and receive it in your new email account.

Enabling SMTP Encryption with Let's Encrypt Certificates

One of the greatest safety precautions is switching on SMS encryption for all of your emails. This makes sure that nobody else but the intended recipient may read the messages you send. This section will guide you through the SMS encryption process using Postfix smtp server with Let's Encrypt issued certificates on Linux servers.

Installing Certbot For SSL Certificate Management

If you want to help protect your SMTP communications with encryption using the Let's Encrypt certificates, the very first step is to install Certbot. In a nutshell, it is a software which can be used easily and handled efficiently to get and manage TLS certificates. Since Let's Encrypt is a totally free open CA, which provides SSL/TLS certificates, so Certbot will suit its purpose just well.

So, in order to get started, please follow the guide on installing Certbot on Linux server below:

Press the terminal and type in the following to add the repository for Certbot:

sudo add-apt-repository ppa:certbot/certbot

Next you would want to run the update command so as to get the packages list updated:

sudo apt-get update

And finally install certbot using the command below:

sudo apt-get install certbot

Configuring Postfix To Use SSL Certificates

With the Certbot installed, what is required next is to reconfigure Postfix to make use of Certbot for the purposes of encrypted connections while transmitting emails. As a result, you will need to reconfigure certain entries in the Postfix main configuration file.

In order to configure postfix for encrypted connections, do the following:

Using a text editor, open the postfix main configuration file. The path is usually found at /etc/postfix/main.cf.

Follow these steps to find the required lines:

#smtpd_tls_cert_file = /etc/ssl/certs/postfix.pem

#smtpd_tls_key_file = /etc/ssl/private/postfix.key

Next, update the paths with the Let's Encrypt certificates obtained with Certbot and uncomment the previously commented lines by removing the “#” symbol before them. The final result should look like this:

smtpd_tls_cert_file = /etc/letsencrypt/live/example.com/fullchain.pem

smtpd_tls_key_file = /etc/letsencrypt/live/example.com/privkey.pem

Now, save the configuration changes and exit the text editor.

Finally, restart the postfix service for the changes to be implemented by executing the following command:

sudo systemctl restart postfix

You have now added the last configuration to secure your email communications with the use of the SMTP encryption Postfix Let’s encrypt certificates. Your email communications privacy and integrity have now been secured.

Enhancing the functionality of Postfix and customization

Postfix is built with several high-level features and customization capabilities that enable users to configure their mail servers according to their requirements. In this subsection we will cover some of these features for instance how to create Maildir email boxes to structure and store emails better and how to configure IMAP with the courier so you can access emails from remote locations.

Creating Maildir folders

Maildir is a widely used email format with links and contact number, that overcomes the limitations of traditional mailbox formats. With Maildir, all mails in an inbox are filed within the relevant message more easily. To create Maildir mailboxes in postfix do these:

Create a new directory for storing the email folders. For example, we can create a directory mail in user’s home directory.

/home/user/mail

Also for each mailbox within the mail folder create sub folders. For instance, create sub folders such as inbox, sent, and drafts to name a few.

/home/user/mail/inbox /home/user/mail/sent

/home/user/mail/drafts

Lastly, edit the postfix configuration file, (main.cf file), to include Mail dir mail folders. In order to direct the folders use the home_mailbox option to the right location.

home_mailbox = Maildir/

Setting Up IMAP Support with Courier

IMAP also provides the user with the ability to view their email messages without the need of downloading them on their respective devices. This means that by adding IMAP support with Courier in Postfix, users will be able to use more than one device at once and still manage their emails effortlessly. If you wish to add IMAP support with Courier then please follow these steps:

Add the Courier – IMAP package in your system.

sudo apt-get install courier-imap

To add IMAP support and edit the Courier-IMAP configuration file (imapd), follow these instructions carefully.

```sudo nano /etc/courier/imapd```

In the file, IMAPDSTART should be changed to IMAPDSTART=ENABLED under the start section.

After saving changes to the file, you can exit the editor and then restart the Courier-IMAP service by executing the command: `sudo service courier-imap restart`

Successfully completing Maildir mailboxes integration intended to efficiently store and organize emails with a much needed IMAP support for better email access served by Courier is the key objective of the above discussed steps. Customize and enhance your mail server to meet your specific requirements and optimize the email experience for you and your users.

Linux Postfix Mail Server Installation Service

Our team of Linux experts is committed in helping you setup your mail server free of spam. With Postfix configured on your server, we ensure that a proper reverse DNS lookup is created to allow your server to receive mail from your IP. Our initiative is to focus in meeting all demand of our customers while at the same time accepting the reality of an absolute zero spam organization to be impossible. With us, you can expect an ideal reverse DNS setup which will guarantee the least number of spam limit by retaining it in the range of thirty fifty mails a day.

Setting up a trustworthy email system is possible thanks to our Linux Postfix Mail Server Setup Service. Enlisting the assistance of our professionals, the first step will consist of installing and testing Postfix, arguably the most widely used mail transfer agent (MTA) server. After sending some external emails to check the functionality of the Postfix email server, the external email can also be sent using the mail command. The team will work to ensure your Postfix server is fully defined to perform the sending and receiving of emails via the simple mail transfer protocol (SMTP). By following our guidance, you will be able to specify parameters for Postfix to apply Strong Email Encryption for incoming and outgoing emails. This way all the email exchanges would become much cleaner and trustworthy.

With our help, you can have a working Ubuntu 20.04 server that uses the Linux Postfix mail server without much trouble. Firstly, we shall proceed to install Postfix on your server so that it can be able to receive emails. After that, step two will allow you to add the IP Address for the server which shall be used for email services. In the third step, we will help you configure the Ubuntu 18.04 server that uses the Postfix mail server to send emails. In the last step, if you have done everything correctly and there are no settings got wrong, your mail server should be online and working perfectly. Rely on us for your Postfix mail server setup and we will save you time and resources while providing you efficient mail services.

Should you seek competent support to get your Linux Postfix mail server fully operational, please look no further as we put at your disposal our Linux Postfix Mail Server Setup Service. We understand that the setup itself may be time-consuming, so we make necessary preparations beforehand, ensuring that everything goes according to the plan. Have no time configuring SMTP servers or email servers? Don’t worry, we’ve got you covered.

Summary

Outro conclusion also has something of harm because the very last point mentioned about configuring a Postfix computer proves to be one of the primal points when trying to figure out setting the mail server side up which is quite a challenging task, however quite straight forward to accomplish. You also make sure to Master the setup as efficiently as you anticipate however until the server side is in place trouble gets easier through everything served with TLS encryption.

In case the end goals include creating a mail server at an organizational level be sure to master these settings. It is however recommended to build the TLS encrypted email server maintaining the best possible security of your email, forwards and other communication.

It is in essence advisable to practice sending different signed email configurations through the command line as it can easily give you the know-how to set up additional features on the master server like authenticating through SMTP and using forwarded emails and finally learn how to self-diagnose when things go wrong while getting set up.

And don't get discouraged when things are hard at first, because practice will make it better. With hands-on experience managing Postfix, you will get used to configuring the mail server for your personal requirements. All you need is time and effort, and soon enough, you will master the art of being a Linux Postfix mail server administrator.