In previous articles, we discussed how to set up your own mail server on Ubuntu from scratch. In part 1 and part 2 of this tutorial series, we learned how to set up Postfix SMTP server and Dovecot IMAP server, but so far we can only have email addresses for users with local Unix accounts. This tutorial is going to show you how to create virtual mailboxes on Ubuntu 20.04 mail server with PostfixAdmin, which is an open-source web-based interface to configure and manage a Postfix based email server for many domains and users.
With virtual mailboxes, we don’t need to create a local Unix account for each email address. If you are going to set up a mail server for a company or organization, it’s always better to have an easy way to create virtual mailboxes in a web-based interface, which also allows users to change their passwords. That’s where PostfixAdmin comes in.
PostfixAdmin Features
- manage mailboxes, virtual domains and aliases
- vacation/out-of-office messages
- alias domains (forwarding one domain to another with recipient validation)
- users can manage their own mailbox (change alias, password and vacation message)
- quota support for single mailboxes and total quota of a domain
- display used quota
- fetchmail integration: You can fetch emails from your original email address to your new email address.
- command line client postfixadmin-cli for those who don’t want to click around in a web interface 😉
Note: Once you finish part 3, you can no longer use local Unix accounts as email addresses. You must create email addresses from the PostfixAdmin web interface.
Prerequisites
It’s required that you have followed part 1 and part 2 of this tutorial series before continuing reading this article. If you followed mail server tutorials on other websites, I recommend purging your configurations and start over with my tutorial series, so you are not going to be confused by different setup processes.
PostfixAdmin is written in PHP and requires a database (MySQL/MariaDB, PostgreSQL or SQLite). This article will use MariaDB database. You also need to run Apache or Nginx web server. So basically we are going to need a LAMP or LEMP stack.
If you prefer to use Apache web server, then set up a LAMP stack.
If you prefer to use Nginx web server, then set up a LEMP stack.
Once the above requirements are met, let’s install and configure PostfixAdmin.
Step 1: Install PostfixAdmin on Ubuntu 20.04 Server
Log into your mail server and install PostfixAdmin from the default Ubuntu software repository.
sudo apt install postfixadmin
During the installation, you will be asked if you want dbconfig-common to configure the database. Choose Yes.
Then select the default database type: mysql.
Dbconfig-common will create the postfixadmin database and user. You need to set a password for this user. Note that the password should not contain the # character, or you might not be able to log in later.
After PostfixAdmin is installed, you can log in to MySQL/MariaDB console with the following command. You will need to enter the password for the postfixadmin user.
mysql -u postfixadmin -p
And you can check what databases the user has permissions to access with the following command.
SHOW DATABASES;
Output:
-------------------- | Database | -------------------- | information_schema | | postfixadmin | -------------------- 2 rows in set (0.002 sec)
By default, the postfixadmin database contains no tables. You can log out of the MySQL/MariaDB console with the following command.
EXIT;
The installation will also create two configuration files: /etc/dbconfig-common/postfixadmin.conf and /etc/postfixadmin/dbconfig.inc.php, both of which contain the database access settings, including the database username and password. Note that if you use MariaDB instead of MySQL, you need to change the database type from mysql to mysqli in both of the two files.
The web files are installed under /usr/share/postfixadmin/ directory, which is owned by root. PostfixAdmin requires a templates_c directory, so create it.
sudo mkdir /usr/share/postfixadmin/templates_c
We need to give www-data user read, write and execute permissions on this directory with the following command.
sudo setfacl -R -m u:www-data:rwx /usr/share/postfixadmin/templates_c/
Step 2: Create Apache Virtual Host or Nginx Config File for PostfixAdmin
Apache
If you use Apache web server, create a virtual host for PostfixAdmin.
sudo nano /etc/apache2/sites-available/postfixadmin.conf
Put the following text into the file. Replace postfixadmin.example.com with your real domain name and don’t forget to set DNS A record for it.
ServerName postfixadmin.example.com
DocumentRoot /usr/share/postfixadmin/public
ErrorLog ${APACHE_LOG_DIR}/postfixadmin_error.log
CustomLog ${APACHE_LOG_DIR}/postfixadmin_access.log combined
Options FollowSymLinks
AllowOverride All
Options FollowSymLinks MultiViews
AllowOverride All
Order allow,deny
allow from all
Save and close the file. Then enable this virtual host with:
sudo a2ensite postfixadmin.conf
Reload Apache for the changes to take effect.
sudo systemctl reload apache2
Now you should be able to see the PostfixAdmin web-based install wizard at http://postfixadmin.example.com/setup.php.
Nginx
If you use Nginx web server, create a virtual host for PostfixAdmin.
sudo nano /etc/nginx/conf.d/postfixadmin.conf
Put the following text into the file. Replace postfixadmin.example.com with your real domain name and don’t forget to set DNS A record for it.
server {
listen 80;
server_name postfixadmin.example.com;
root /usr/share/postfixadmin/public/;
index index.php index.html;
access_log /var/log/nginx/postfixadmin_access.log;
error_log /var/log/nginx/postfixadmin_error.log;
location / {
try_files $uri $uri/ /index.php;
}
location ~ ^/(. .php)$ {
try_files $uri =404;
fastcgi_pass unix:/run/php/php7.4-fpm.sock;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
include /etc/nginx/fastcgi_params;
}
}
Save and close the file. Then test Nginx configuration.
sudo nginx -t
If the test is successful, reload Nginx for the changes to take effect.
sudo systemctl reload nginx
Now you should be able to see the PostfixAdmin web-based install wizard at http://postfixadmin.example.com/setup.php.
Step 3: Install Required and Recommended PHP Modules
Run the following command to install PHP modules required or recommended by PostfixAdmin.
sudo apt install php7.4-fpm php7.4-imap php7.4-mbstring php7.4-mysql php7.4-json php7.4-curl php7.4-zip php7.4-xml php7.4-bz2 php7.4-intl php7.4-gmp
Then restart Apache. (If you use Nginx, you don’t need to restart Nginx.)
sudo systemctl restart apache2
Step 4: Enabling HTTPS
To encrypt the HTTP traffic, we can enable HTTPS by installing a free TLS certificate issued from Let’s Encrypt. Run the following command to install Let’s Encrypt client (certbot) on Ubuntu 20.04 server.
sudo apt install certbot
If you use Apache, install the Certbot Apache plugin.
sudo apt install python3-certbot-apache
And run this command to obtain and install TLS certificate.
sudo certbot --apache --agree-tos --redirect --hsts --staple-ocsp --email [email protected] -d postfixadmin.example.com
If you use Nginx, then you also need to install the Certbot Nginx plugin.
sudo apt install python3-certbot-nginx
Next, run the following command to obtain and install TLS certificate.
sudo certbot --nginx --agree-tos --redirect --hsts --staple-ocsp --email [email protected] -d postfixadmin.example.com
Where
--nginx: Use the nginx plugin.--apache: Use the Apache plugin.--agree-tos: Agree to terms of service.--redirect: Force HTTPS by 301 redirect.--hsts: Add the Strict-Transport-Security header to every HTTP response. Forcing browser to always use TLS for the domain. Defends against SSL/TLS Stripping.--staple-ocsp: Enables OCSP Stapling. A valid OCSP response is stapled to the certificate that the server offers during TLS.
The certificate should now be obtained and automatically installed, which is indicated by the message below.
Step 5: Use Strong Password Scheme in PostfixAdmin and Dovecot
By default, PostfixAdmin and Dovecot use MD5-CRYPT, which is a weak password scheme. You can list available password schemes in Dovecot with the following command.
sudo doveadm pw -l
Sample output:
SHA1 SSHA512 BLF-CRYPT PLAIN HMAC-MD5 OTP SHA512 SHA RPA DES-CRYPT CRYPT SSHA MD5-CRYPT SKEY PLAIN-MD4 PLAIN-MD5 SCRAM-SHA-1 LANMAN SHA512-CRYPT CLEAR CLEARTEXT ARGON2I ARGON2ID SSHA256 NTLM MD5 PBKDF2 SHA256 CRAM-MD5 PLAIN-TRUNC SHA256-CRYPT SMD5 DIGEST-MD5 LDAP-MD5
Argon2 is a fairly strong password scheme. To use it, we need to edit the PostfixAdmin configuration file, which by default is /usr/share/postfixadmin/config.inc.php, but we can create a separate file (config.local.php) to store our modifications, so they won’t be overriden when a new version of PostfixAdmin is installed in the future.
sudo nano /usr/share/postfixadmin/config.local.php
Add the following lines in the file to use Argon2 password scheme.
$CONF['encrypt'] = 'dovecot:ARGON2I';
$CONF['dovecotpw'] = "https://www.linuxbabe.com/usr/bin/doveadm pw -r 5";
if(@file_exists('/usr/bin/doveadm')) { // @ to silence openbase_dir stuff; see https://github.com/postfixadmin/postfixadmin/issues/171
$CONF['dovecotpw'] = "https://www.linuxbabe.com/usr/bin/doveadm pw -r 5"; # debian
}
Save and close the file. We will configure password scheme for Dovecot in step 9.
Step 6: Finish the Installation in Web Browser
Go to postfixadmin.example.com/setup.php to run the web-based setup wizard. First, it will check if all dependencies are installed.
If you see the following error,
Invalid query: Specified key was too long; max key length is 1000 bytes
Then you need to log in to MySQL/MariaDB database server as root from command line,
sudo mysql -u root
and change the default collation from utf8mb4_general_ci to utf8_general_ci.
MariaDB [(none)]> alter database postfixadmin collate ='utf8_general_ci';
Exit MySQL/MariaDB console and reload the setup.php page. Once all requirements are satisfied, you can create a setup password for PostfixAdmin.
After creating the password hash, you need to open the /etc/postfixadmin/config.inc.php file to update the password hash. Replace changeme with your own password hash.
$CONF['setup_password'] = 'changeme';
Next, create the admin account.
After that, you can log into PostfixAdmin at postfixadmin.example.com/login.php.
Step 7: Checking Tables in the Database
The PostfixAdmin setup process populates the postfixadmin database with some default tables. It’s helpful for us to know the names and structure of the tables. Log in to MySQL/MariaDB console.
sudo mysql -u root
Select the postfixadmin database.
USE postfixadmin;
List all tables in this database.
SHOW TABLES;
Output:
------------------------ | Tables_in_postfixadmin | ------------------------ | admin | | alias | | alias_domain | | config | | domain | | domain_admins | | fetchmail | | log | | mailbox | | quota | | quota2 | | vacation | | vacation_notification | ------------------------ 13 rows in set (0.001 sec)
The 3 most important tables are:
domain: contains information on the domains that are using your mail server to send and receive email.mailbox: contains information on every email address, including hashed password and the location of mail files.alias: contains the alias of each email address.
If you are interested, you can check what columns each table contains. For example, the following command will show us the columns in the domain table.
DESCRIBE domain;
Output:
------------- -------------- ------ ----- --------------------- ------- | Field | Type | Null | Key | Default | Extra | ------------- -------------- ------ ----- --------------------- ------- | domain | varchar(255) | NO | PRI | NULL | | | description | varchar(255) | NO | | NULL | | | aliases | int(10) | NO | | 0 | | | mailboxes | int(10) | NO | | 0 | | | maxquota | bigint(20) | NO | | 0 | | | quota | bigint(20) | NO | | 0 | | | transport | varchar(255) | NO | | NULL | | | backupmx | tinyint(1) | NO | | 0 | | | created | datetime | NO | | 2000-01-01 00:00:00 | | | modified | datetime | NO | | 2000-01-01 00:00:00 | | | active | tinyint(1) | NO | | 1 | | ------------- -------------- ------ ----- --------------------- -------
Log out of MySQL/MariaDB console.
EXIT;
Step 8: Configure Postfix to Use MySQL/MariaDB Database
By default, Postfix delivers emails only to users with a local Unix account. To make it deliver emails to virtual users whose information is stored in the database, we need to configure Postfix to use virtual mailbox domains.
First, we need to add MySQL map support for Postfix by installing the postfix-mysql package.
sudo apt install postfix-mysql
Then edit the Postfix main configuration file.
sudo nano /etc/postfix/main.cf
Add the following lines at the end of this file.
virtual_mailbox_domains = proxy:mysql:/etc/postfix/sql/mysql_virtual_domains_maps.cf virtual_mailbox_maps = proxy:mysql:/etc/postfix/sql/mysql_virtual_mailbox_maps.cf, proxy:mysql:/etc/postfix/sql/mysql_virtual_alias_domain_mailbox_maps.cf virtual_alias_maps = proxy:mysql:/etc/postfix/sql/mysql_virtual_alias_maps.cf, proxy:mysql:/etc/postfix/sql/mysql_virtual_alias_domain_maps.cf, proxy:mysql:/etc/postfix/sql/mysql_virtual_alias_domain_catchall_maps.cf
Where:
virtual_mailbox_domainspoints to a file that will tell Postfix how to look up domain information from the database.virtual_mailbox_mapspoints to files that will tell Postfix how to look up email addresses from the database.virtual_alias_mapspoints to files that will tell Postfix how to look up aliases from the database.
We want to use dovecot to deliver incoming emails to the virtual users’ message store, so add the following line.
virtual_transport = lmtp:unix:private/dovecot-lmtp
Save and close the file. Next, we need to create the .cf files one by one. Create the sql directory.
sudo mkdir /etc/postfix/sql/
Create the mysql_virtual_domains_maps.cf file.
sudo nano /etc/postfix/sql/mysql_virtual_domains_maps.cf
Add the following content. Replace password with the postfixadmin password you set in Step 1.
user = postfixadmin
password = password
hosts = localhost
dbname = postfixadmin
query = SELECT domain FROM domain WHERE domain='%s' AND active = '1'
#query = SELECT domain FROM domain WHERE domain='%s'
#optional query to use when relaying for backup MX
#query = SELECT domain FROM domain WHERE domain='%s' AND backupmx = '0' AND active = '1'
#expansion_limit = 100
Create the mysql_virtual_mailbox_maps.cf file.
sudo nano /etc/postfix/sql/mysql_virtual_mailbox_maps.cf
Add the following content.
user = postfixadmin
password = password
hosts = localhost
dbname = postfixadmin
query = SELECT maildir FROM mailbox WHERE username='%s' AND active = '1'
#expansion_limit = 100
Create the mysql_virtual_alias_domain_mailbox_maps.cf file.
sudo nano /etc/postfix/sql/mysql_virtual_alias_domain_mailbox_maps.cf
Add the following content.
user = postfixadmin
password = password
hosts = localhost
dbname = postfixadmin
query = SELECT maildir FROM mailbox,alias_domain WHERE alias_domain.alias_domain = '%d' and mailbox.username = CONCAT('%u', '@', alias_domain.target_domain) AND mailbox.active = 1 AND alias_domain.active='1'
Create the mysql_virtual_alias_maps.cf file.
sudo nano /etc/postfix/sql/mysql_virtual_alias_maps.cf
Add the following content.
user = postfixadmin
password = password
hosts = localhost
dbname = postfixadmin
query = SELECT goto FROM alias WHERE address='%s' AND active = '1'
#expansion_limit = 100
Create the mysql_virtual_alias_domain_maps.cf file.
sudo nano /etc/postfix/sql/mysql_virtual_alias_domain_maps.cf
Add the following content.
user = postfixadmin
password = password
hosts = localhost
dbname = postfixadmin
query = SELECT goto FROM alias,alias_domain WHERE alias_domain.alias_domain = '%d' and alias.address = CONCAT('%u', '@', alias_domain.target_domain) AND alias.active = 1 AND alias_domain.active='1'
Create the mysql_virtual_alias_domain_catchall_maps file.
sudo nano /etc/postfix/sql/mysql_virtual_alias_domain_catchall_maps.cf
Add the following content.
# handles catch-all settings of target-domain
user = postfixadmin
password = password
hosts = localhost
dbname = postfixadmin
query = SELECT goto FROM alias,alias_domain WHERE alias_domain.alias_domain = '%d' and alias.address = CONCAT('@', alias_domain.target_domain) AND alias.active = 1 AND alias_domain.active='1'
Since the database passwords are stored in plain text so they should be readable only by user postfix and root, which is done by executing the following two commands.
sudo chmod 0640 /etc/postfix/sql/* sudo setfacl -R -m u:postfix:rx /etc/postfix/sql/
Now let’s open the Postfix main configuration file again.
sudo nano /etc/postfix/main.cf
Find the mydestination parameter, which contains a list of domain names that will receive emails delivered to local Unix accounts. Since we are going to use virtual mailbox, so we need to remove the apex domain name from the list. My apex domain name is linuxbabe.com, so I removed it from the mydestination parameter.
mydestination = $myhostname, mail.linuxbabe.com, localhost.linuxbabe.com, localhost
Then add the following lines at the end of this file.
virtual_mailbox_base = /var/vmail virtual_minimum_uid = 2000 virtual_uid_maps = static:2000 virtual_gid_maps = static:2000
The first line defines the base location of mail files. The remaining 3 lines define which user ID and group ID Postfix will use when delivering incoming emails to the mailbox. We use the user ID 2000 and group ID 2000.
Save and close the file. Restart Postfix for the changes to take effect.
sudo systemctl restart postfix
Next, we need to create a user named vmail with ID 2000 and a group with ID 2000.
sudo adduser vmail --uid 2000 --disabled-login --disabled-password
Create the mail base location.
sudo mkdir /var/vmail/
Make vmail as the owner.
sudo chown vmail:vmail /var/vmail/ -R
Step 9: Configure Dovecot to Use MySQL/MariaDB Database
We also need to configure the Dovecot IMAP server to query user information from the database. First, run the following command to add MySQL support for Dovecot.
sudo apt install dovecot-mysql
Then edit the 10-mail.conf file.
sudo nano /etc/dovecot/conf.d/10-mail.conf
In part 2, we used the default mail_location.
mail_location = mbox:~/mail:INBOX=/var/mail/%u
Since we are using virtual mailbox domain now, we need to change the mail_location to:
mail_location = maildir:/var/vmail/%d/%n
Edit the 10-auth.conf file.
sudo nano /etc/dovecot/conf.d/10-auth.conf
In part 2, we used the following value for auth_username_format.
auth_username_format = %n
The %n would drop away the domain if it was given. Because in part 2 we were using local Unix account for the username of every email address, we must use %n to drop away the domain, so users were able to login with the full email address.
Now we are using virtual mailbox domains, which means the username of every email address includes the domain part, so we need to change the auth_username_format as follows. %u won’t drop away the domain. This allows users to login with the full email address.
auth_username_format = %u
Uncomment the following line at the end of this file, so Dovecot can query user information from the database.
!include auth-sql.conf.ext
It can be helpful to add the following two lines in this file to debug login issues. The login errors would be logged into /var/log/mail.log file. (Once users can login without problems, you can comment out the following two lines.)
auth_debug = yes auth_debug_passwords = yes
Edit the dovecot-sql.conf.ext file.
sudo nano /etc/dovecot/dovecot-sql.conf.ext
Here is the content that you should have. Replace password with the postfixadmin password you set in Step 1.
driver = mysql
connect = host=localhost dbname=postfixadmin user=postfixadmin password=password
default_pass_scheme = ARGON2I
password_query = SELECT username AS user,password FROM mailbox WHERE username = '%u' AND active='1'
user_query = SELECT maildir, 2000 AS uid, 2000 AS gid FROM mailbox WHERE username = '%u' AND active='1'
iterate_query = SELECT username AS user FROM mailbox
Restart Dovecot.
sudo systemctl restart dovecot
When a user tries to log in, Dovecot would use the Argon2 algorithm to generate a password hash from the password entered by the user, then compare it with the password hash stored in the database.
Step 10: Add Domain and Mailboxes in PostfixAdmin
Log in to PostfixAdmin web interface as the admin. Click the Domain List tab and select New Domain to add a domain. You can choose how many aliases and mailboxes are allowed for this domain.
Then click Virtual List tab and select Add Mailbox to add a new email address for your domain.
Next, you can open your desktop email client such as Mozilla Thunderbird and add a mail account.
- In the incoming server section, select IMAP protocol, enter
mail.your-domain.comas the server name, choose port 143 and STARTTLS. Choosenormal passwordas the authentication method. - In the outgoing section, select SMTP protocol, enter
mail.your-domain.comas the server name, choose port 587 and STARTTLS. Choosenormal passwordas the authentication method.
You should now be able to connect to your own email server and also send and receive emails with your desktop email client! Note that you cannot use local Unix accounts to login now. You must log in with the virtual user created from PostfixAdmin web interface.
Change User Password in PostfixAdmin
Users can log into PostfixAdmin at https://postfixadmin.example.com/users/login.php, then change their passwords.
Next Step
I hope this tutorial helped you install and use PostfixAdmin on Ubuntu 20.04 to create virtual mailboxes. In part 4, I will show you how to set up SPF and DKIM with Postfix to improve email deliverability and in a future tutorial, I’m going to show you how to host multiple domains with PostfixAdmin. As always, if you found this post useful, subscribe to our free newsletter to get more tips and tricks. Take care 🙂
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