Sending e-mails with Postfix
by Uday R. Sawant, William Leemans, Jonathan Hobson, Oliver Pelz
Linux: Powerful Server Administration
- Linux: Powerful Server Administration
- Table of Contents
- Linux: Powerful Server Administration
- Linux: Powerful Server Administration
- Credits
- Preface
- 1. Module 1
- 1. Managing Users and Groups
- 2. Networking
- Introduction
- Connecting to a network with a static IP
- Installing the DHCP server
- Installing the DNS server
- Hiding behind the proxy with squid
- Being on time with NTP
- Discussing load balancing with HAProxy
- Tuning the TCP stack
- Troubleshooting network connectivity
- Securing remote access with OpenVPN
- Securing a network with uncomplicated firewall
- Securing against brute force attacks
- Discussing Ubuntu security best practices
- 3. Working with Web Servers
- Introduction
- Installing and configuring the Apache web server
- Serving dynamic contents with PHP
- Hosting multiple websites with a virtual domain
- Securing web traffic with HTTPS
- Installing Nginx with PHP_FPM
- Setting Nginx as a reverse proxy
- Load balancing with Nginx
- Setting HTTPs on Nginx
- Benchmarking and performance tuning of Apache
- Securing the web server
- Troubleshooting the web server
- 4. Working with Mail Servers
- 5. Handling Databases
- Introduction
- Installing relational databases with MySQL
- Storing and retrieving data with MySQL
- Importing and exporting bulk data
- Adding users and assigning access rights
- Installing web access for MySQL
- Setting backups
- Optimizing MySQL performance – queries
- Optimizing MySQL performance – configuration
- Creating MySQL replicas for scaling and high availability
- Troubleshooting MySQL
- Installing MongoDB
- Storing and retrieving data with MongoDB
- 6. Network Storage
- 7. Cloud Computing
- 8. Working with Containers
- Introduction
- Installing LXD, the Linux container daemon
- Deploying your first container with LXD
- Managing LXD containers
- Managing LXD containers – advanced options
- Setting resource limits on LXD containers
- Networking with LXD
- Installing Docker
- Starting and managing Docker containers
- Creating images with a Dockerfile
- Understanding Docker volumes
- Deploying WordPress using a Docker network
- Monitoring Docker containers
- Securing Docker containers
- 9. Streaming with Ampache
- 10. Communication Server with XMPP
- 11. Git Hosting
- Introduction
- Installing Git
- Creating a local repository with Git CLI
- Storing file revisions with Git commit
- Synchronizing the repository with a remote server
- Receiving updates with Git pull
- Creating repository clones
- Installing GitLab, your own Git hosting
- Adding users to the GitLab server
- Creating a repository with GitLab
- Automating common tasks with Git hooks
- 12. Collaboration Tools
- 13. Performance Monitoring
- 14. Centralized Authentication Service
- 2. Module 2
- 1. Installing CentOS
- Introduction
- Downloading CentOS and confirming the checksum on Windows or OS X
- Creating USB installation media on Windows or OS X
- Performing an installation of CentOS using the graphical installer
- Running a netinstall over HTTP
- Installing CentOS 7 using a kickstart file
- Getting started and customising the boot loader
- Troubleshooting the system in rescue mode
- Updating the installation and enhancing the minimal install with additional administration and development tools
- 2. Configuring the System
- Introduction
- Navigating text files with less
- Introduction to Vim
- Speaking the right language
- Synchronizing the system clock with NTP and the chrony suite
- Setting your hostname and resolving the network
- Building a static network connection
- Becoming a superuser
- Customizing your system banners and messages
- Priming the kernel
- 3. Managing the System
- Introduction
- Knowing and managing your background services
- Troubleshooting background services
- Tracking system resources with journald
- Configuring journald to make it persistent
- Managing users and their groups
- Scheduling tasks with cron
- Synchronizing files and doing more with rsync
- Maintaining backups and taking snapshots
- Monitoring important server infrastructure
- Taking control with GIT and Subversion
- 4. Managing Packages with YUM
- 5. Administering the Filesystem
- 6. Providing Security
- 7. Building a Network
- 8. Working with FTP
- 9. Working with Domains
- 10. Working with Databases
- 11. Providing Mail Services
- 12. Providing Web Services
- 13. Operating System-Level Virtualization
- 14. Working with SELinux
- 15. Monitoring IT Infrastructure
- 1. Installing CentOS
- 3. Module 3
- 1. Working with KVM Guests
- 2. Deploying RHEL "En Masse"
- 3. Configuring Your Network
- 4. Configuring Your New System
- 5. Using SELinux
- 6. Orchestrating with Ansible
- 7. Puppet Configuration Management
- 8. Yum and Repositories
- 9. Securing RHEL 7
- 10. Monitoring and Performance Tuning
- Bibliography
- Index
In this recipe, we will set up Postfix Mail Transfer Agent (MTA). This will be a very basic setup which will enable us to send and receive e-mails from our server. Postfix is an open source MTA which routes e-mails to their destination. It is a default MTA for Ubuntu and is available in Ubuntu's main package repository.
You will need access to a root account or an account with sudo privileges.
A domain name (FQDN) is required while configuring Postfix. You can configure your local server for testing, but make sure that you set the proper host entries and hostname.
Follow these steps to send e-mails with Postfix:
- Install Postfix and
mailutilswith the following commands:$ sudo apt-get update $ sudo apt-get install postfix mailutils -y
- The installation process will prompt you to enter some basic configuration details. When asked for General type of mail configuration:, select Internet Site and then click on <Ok>:
- On the next screen, enter your domain name, for example,
mail.example.com, and answer the other questions. You can leave them with default values:
- After installation completes, we need to modify the Postfix configuration under
/etc/postfix/main.cf:$ sudo nano /etc/postfix/main.cf - Set
myhostnameto point to your domain name:myhostname = mail.example.com - Ensure
mynetworksis set to the local network. This will secure your server from spammers:mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
- Also check
mydestination. It should contain your domain name:mydestination = example.com, ubuntu, localhost.localdoma in, localhost
- Change the mail storage format to
Maildirfrom the defaultmbox. Search and uncomment the following line:home_mailbox = Maildir/ - Optionally, you can change the TLS keys used by Postfix. Find the
TLS parameterssection and point the variables to your key path:
- Save the configuration file and exit.
- Now, reload Postfix for the changes to take effect:
$ sudo service postfix reloadTest if everything is working as expected. Open a telnet connection to the mail server:
$ telnet localhost 25You should see an output similar to the following screenshot:
- Now, send your first e-mail from this server. Type
sendmail user@domainand press Enter. Then, type your message, and when done with that press Ctrl + D to send an e-mail. - To read your e-mails, log in with the user you send e-mails to. Start the mail program with the command
mail. This should show you a list of e-mails received by this user account. The output should look similar to following screenshot:
- To read any e-mail, type in the mail number and press Enter. Type
qfollowed by Enter to quit the mail reader.
Postfix installation is quite a simple task; you need to be sure that you have configured the proper settings and then you are up and running in minutes. The Postfix installation process itself prompts for basic settings.
Other parameters include mynetworks and mydestination. With mynetwork, we have restricted the uses of the mail server to the local network. Only users on the local network can use this server to send and receive e-mails. The parameter mydestination specifies the domain names that Postfix is going to serve. For all other domains that are not listed under mydestination, Postfix will simply act as a forwarder.
We have configured Postfix to use the Maildir format for storing e-mails. This is a new storage format and provides various improvements over the default format, mbox. Also, Maildir is used by various IMAP and POP servers. With Maildir, each new message is stored in a separate file. This avoids file locking when working with messages and provides protection against mailbox corruption.
Now if you send an e-mail to a local domain, it will be delivered to the inbox of the respective user, which can be read with mail command. If you send e-mails to an external mail server, such as Gmail, chances are your mail gets delivered to spam. You need to include a number of different parameters in your e-mail headers and then make sure that your server IP is not blacklisted. It would be a good idea to use an external mail server such as Mail Chimp or Gmail for sending e-mails.
- An article by Jeff Atwood on sending e-mails through code. This may help you get your e-mails out of spam: http://blog.codinghorror.com/so-youd-like-to-send-some-email-through-code/
- Mailbox formats: http://wiki.dovecot.org/MailboxFormat
- The difference between port 465 and 587: http://stackoverflow.com/questions/15796530/what-is-the-difference-between-ports-465-and-587
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