Adding e-mail accounts
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 learn how to add e-mail accounts to Postfix. The easiest way to add a new e-mail account to Postfix is to add a new user account on your server. Postfix will check for user accounts and deliver e-mails to respective users. We will create a virtual user setup so that we do not need to create user accounts for each e-mail user.
You will need access to a root account or an account with sudo privileges.
I assume that you have completed your basic Postfix setup and that it is working properly.
Follow these steps to add e-mail account:
- Create a new user account:
$ useradd -s /usr/bin/nologin -m vmail - Get the UID and GID for this account:
$ grep vmail /etc/passwd vmail:x:1001:1001::/home/vmail:/usr/bin/nologin
- Create a base directory layout for domains and users:
$ sudo mkdir -p /home/vmail/example.org/bob $ sudo mkdir -p /home/vmail/example.net/alice
- Allow only the user vmail to access these files:
$ sudo chown -R vmail:vmail /home/vmail $ chmod -R 700 /home/vmail
- Next, configure Postfix. Edit
/etc/postfix/main.cfand add the following lines:virtual_mailbox_base = /home/vmail virtual_mailbox_domains = /etc/postfix/virtual_domains virtual_mailbox_maps = hash:/etc/postfix/virtual_maps virtual_alias_maps = hash:/etc/postfix/virtual_alias virtual_uid_maps = static:1001 # user ID for user vmail virtual_gid_maps = static:1001 # group ID for user vmail
- Create the file
virtual_domainsunder/etc/postfix:$ sudo nano /etc/postfix/virtual_domainsexample.org example.net
- Create the
virtual_mapsfile:$ sudo nano /etc/postfix/virtual_maps [email protected] example.org/bob/ [email protected] example.org/alice/ @example.org example.org/catchall/ # catch all address
- Create the
virtual_aliasfile and optionally set aredirect:$ sudo nano /etc/postfix/virtual_alias # redirect emails for tim to bob [email protected] [email protected]
- Now generate database of virtual maps and aliases by hashing respective files:
$ sudo postmap /etc/postfix/virtual_maps $ sudo postmap /etc/postfix/virtual_alias
- Reload Postfix and send an e-mail to the newly created address:
$ sudo postfix reload $ sendmail [email protected]
Here, we have created a virtual mailbox setup to enable our Postfix server to serve multiple domains as well as add e-mail users without creating user accounts on the server. All e-mails received by virtual users will be stored under the home directory of the vmail user (virtual_mailbox_base in Postfix configuration). When you need to add a new e-mail account, simply add the e-mail address with its respective domain to the virtual_maps file. In case you need to support a new domain, you can easily add it to the virtual_domains file.
The third file we used is virtual_alias. You can set e-mail forwarding in this file. It is handy when you need to create a new alias for an e-mail address or forward e-mails to one or multiple accounts. We have set a catchall entry in the virtual_alias file; this setting will redirect all e-mails received on nonexistent accounts to [email protected], which can be checked by the domain administrator.
Using files for virtual users and domains is good for getting started with setup. But once you need to add more and more user accounts and domains it is a good idea to move the users and domains to a database server. This can be easily done by changing the lookup table type. Postfix supports a variety of lookup table types, which include LDAP, MySQL, PGSQL, memcache, SQLite, and many others.
To use MySQL as a backend database, complete the following steps:
- Create respective tables for
virtual_domain,virtual_maps, andvirtual_alias. - Change the Postfix configuration to use MySQL as a lookup table:
virtual_mailbox_domains = mysql:/etc/postfix/mysql-virtual-domains virtual_mailbox_maps = mysql:/etc/postfix/mysql-virtual-maps virtual_alias_maps = mysql:/etc/postfix/mysql-virtual-alias
- Add the respective details to each file using the following commands:
$ sudo nano /etc/postfix/mysql-virtual-domainsuser = mysql_user password = mysql_password hosts = 127.0.0.1 dbname = mysql_db_name query = SELECT 1 FROM virtual_domains WHERE name='%s' $ sudo nano /etc/postfix/mysql-virtual-maps... query = SELECT 1 FROM virtual_users WHERE email='%s' $ sudo nano /etc/postfix/mysql-virtual-alias... query = SELECT destination FROM virtual_aliases WHERE source='%s'
- You can test your mapping with the following command. This should output
1as a result:$ postmap -q [email protected] mysql:/etc/postfix/mysql-virtual-maps - Finally, restart the Postfix daemon.
The Vimbadmin package provides a web console for virtual mailbox administration. It is a PHP-based open source package. You can get source code and installation instructions at https://github.com/opensolutions/ViMbAdmin.
- Postfix guide at http://www.postfix.org/VIRTUAL_README.html
- Postfix lookup table types at http://www.postfix.org/DATABASE_README.html#types
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