From Postfix's site:
- "Postfix attempts to be fast, easy to administer, and secure, while at the same time being sendmail compatible enough to not upset existing users. Thus, the outside has a sendmail-ish flavor, but the inside is completely different."
The goal of this article is to setup Postfix for virtual mailbox delivery only. There will be no delivery to user accounts on the system (
/etc/passwd). Further, access will only be available via a web mail frontend (Squirrelmail), no direct POP3 or IMAP access will be granted. It should be fairly easy to allow those additional features given the information below, but it is not within the scope of this document.
- 1 Required packages
- 2 Pre-installtion
- 3 Postfix configuration
- 3.1 /etc/postfix/master.cf
- 3.2 /etc/postfix/main.cf
- 3.3 /etc/postfix/aliases
- 3.4 /etc/postfix/virtual_alias
- 3.5 mysql_virtual_domains.cf
- 3.6 mysql_virtual_mailboxes.cf
- 3.7 mysql_virtual_forwards.cf
- 3.8 Postfix check
- 3.9 Start Postfix
- 4 MySQL configuration
- 5 Test Postfix
- 6 Configure Courier IMAP
- 7 Configure Squirrelmail
- 7.1 Create secure http site (https)
- 7.2 put Squirrelmail in the directory you created
- 7.3 run Squirrelmail config utility
- 7.4 test the Squirrelmail setup
- 7.5 test Squirrelmail
- 8 See also
- AUR ( is an officially supported alternative, not yet included in this article) AUR from
- AUR ( is an officially supported alternative, not yet included in this article) AUR from
We need to create the user for storing the virtual mail. Create a vmailuser as follows:
# groupadd -g 5003 vmail # useradd -g vmail -u 5003 -d /home/vmailer -s /bin/false vmailer # mkdir /home/vmailer # chown vmailer:vmail /home/vmailer # chmod -R 750 /home/vmailer # passwd vmailer
5003 UID/GID are the ones specified in the Postfix main.cf file.
setup MX record
An MX record should point to the mail host. Usually this is done from configuration interface of your domain provider.
A mail exchanger record (MX record) is a type of resource record in the Domain Name System that specifies a mail server responsible for accepting email messages on behalf of a recipient's domain.
When an e-mail message is sent through the Internet, the sending mail transfer agent queries the Domain Name System for MX records of each recipient's domain name. This query returns a list of host names of mail exchange servers accepting incoming mail for that domain and their preferences. The sending agent then attempts to establish an SMTP connection to one of these servers, starting with the one with the smallest preference number, delivering the message to the first server with which a connection can be made.
This is the Pipeline configuration file, in which you can put your new pipes e.g. to check for Spam!
For virtual mail
set myhostname if your mail server has multiple domains, and you do not want the primary domain to be the mail host. The default is to use the result of a gethostname() call if nothing is specified. For our purposes we will just set it as follows:
myhostname = mail.nospam.net
This is assuming that a DNS A record, and an MX record both point to mail.nospam.net
this is usually the value of myhostname, minus the first part. If your domain is wonky, then just set it manually:
mydomain = nospam.net
this is where the email will be seen as being sent from. I usually set this to the value of mydomain. For simple servers, this works fine. This is for mail originating from a local account. Since we are not doing local delivery (except sending), then this is not really as important as it normally would be.
myorigin = $mydomain
This is the lookup for local users. Since we are not going to deliver internet mail for any local users, set this to localhost only.
mydestination = localhost
mynetworks and mynetwork_style
Both of these control relaying, and whom is allowed to. We do not want any relaying. For our sakes, we will simply set mynetwork_style to host, as we are trying to make a standalone postfix host, that people with use webmail on. No relaying, no other MTA's. Just webmail.
mynetworks_style = host
This controls the destinations that Postfix will relay TO. The default value is $mydestination. This should be fine for now.
relay_domains = $mydestination
This setting controls how mail is stored for the users. Set this to "Maildir/", as courier IMAP requires Maildir style mail storage. This is a good thing. Maildir format mailboxes remove the possible race conditions that can occur with old style mbox formats. No more need to deal with file locking. The '/' at the end is REQUIRED.
home_mailbox = Maildir/
Virtual mail is mail that does not map to a user account (
/etc/passwd). This is where all the email for the system will be kept. We are not doing local delivery, remember, so if you want a user that has the same name as a local user, just make a virtual account with the same name.
First thing we need to do is add the following:
virtual_mailbox_domains = virtualdomain.tld virtual_alias_maps = hash:/etc/postfix/virtual_alias, mysql:/etc/postfix/mysql_virtual_forwards.cf virtual_mailbox_domains = mysql:/etc/postfix/mysql_virtual_domains.cf virtual_mailbox_maps = mysql:/etc/postfix/mysql_virtual_mailboxes.cf virtual_mailbox_base = /home/vmailer virtual_uid_maps = static:5003 virtual_gid_maps = static:5003 virtual_minimum_uid = 5003 virtual_mailbox_limit = 51200000
virtual_mailbox_domains is a list of the domains that you want to receive mail for. This CANNOT be the same thing that is listed in mydestination. That is why we left mydestination to be localhost only. virtual_mailbox_maps will contain the info about the virtual users and their mailbox locations. We are using a hash file to store the more permanent maps, and these will override the forwards in the MySQL database.
virtual_mailbox_base is the base dir where the virtual mailboxes will be stored. The gid and uid maps are the real system user account that the virtual mail will be owned by. This is for storage purposes. Since we will be using a web interface, and do not want people accessing this by any other means, we will be creating this account later with no login access. Virtual_mailbox_limit controls the size of the mailbox. I do not know how well this works yet. I have set the size above to about 50MB.
Default message and mailbox size limits
Postfix imposes both message and mailbox size limits by default. The message_size_limit controls the maximum size in bytes of a message, including envelope information. (default 10240000) The mailbox_size_limit controls the maximum size of any local individual mailbox or maildir file. This limits the size of any file that is written to upon local delivery, including files written by external commands (i.e. procmail) that are executed by the local delivery agent. (default is 51200000, set to 0 for no limit) If bounced message notifications are generated, check the size of the local mailbox under
/var/spool/mail and use postconf to check these size limits:
supersff:~> postconf -d mailbox_size_limit mailbox_size_limit = 51200000 supersff:~> postconf -d message_size_limit message_size_limit = 10240000
The only things you need to change in
/etc/postfix/main.cf are as follows. Uncomment them and modify them to the specifics listed below. Everything else can be left as installed.
inet_interfaces = loopback-only mynetworks_style = host append_dot_mydomain = no default_transport = error: Local delivery only!
If you want to control where the mail gets delivered and which mailbox format is to be used, you can do this by setting:
home_mailbox = /some/path
mail_spool_directory is an absolute path where all mail goes, while home_mailbox specifies a mailbox relative to the user's home directory. If the path ends with a slash ('/'), messages are stored in Maildir format (directory tree, one message per file); if it doesn't, the mbox format is used (all mail in one file).
mail_spool_directory = /var/mail (1) home_mailbox = Maildir/ (2)
1) All mail will be stored in
/var/mail, mbox format.
2) Mail will be saved in
~/Maildir, Maildir format.
We need to map some aliases to real accounts. The default setup by arch looks pretty good here.
Uncomment the following line, and change it to a real account. I put the user account on the box that I use. Best not to just send mail to root, because you do not want to be logging in as root or checking email as root. Not good. Sudo is your friend, and so is forwarding root mail. Since this is for local delivery only (syslogs and stuff), it is still within the realm of mydestination.
Once you have finished editing
/etc/postfix/aliases you must run the postalias command:
/etc/postfix/virtual_alias with the following contents:
MAILER-DAEMON: postmaster postmaster: root # General redirections for pseudo accounts bin: root daemon: root named: root nobody: root uucp: root www: root ftp-bugs: root postfix: root # Put your local aliases here. # Well-known aliases manager: root dumper: root operator: root abuse: postmaster # trap decode to catch security attacks decode: root # Person who should get root's mail. Don't receive mail as root! root: firstname.lastname@example.org
Then run the postalias command on it:
Alternatively you can create the file .forward in /root. specify the user to whom root mail should be forwarded, e.g. user@localhost.
/etc/postfix/mysql_virtual_domains.cf file with the following (or similar) contents:
user = postfixuser password = XXXXXXXXXX hosts = localhost dbname = postfix table = domains select_field = 'virtual' where_field = domain
Create the /etc/postfix/mysql_virtual_mailboxes.cf file with the following (or similar) contents:
user = postfixuser password = XXXXXXXXXX hosts = localhost dbname = postfix table = users select_field = concat(domain,'/',email,'/') where_field = email
Instead of having a directory structure something like /email@example.com you can have cleaner subdirectories (without the additional domain name) by replacing select_field and where_field with:
query = SELECT CONCAT(SUBSTRING_INDEX(email,'@',-1),'/',SUBSTRING_INDEX(email,'@',1),'/') FROM users WHERE email='%s'
/etc/postfix/mysql_virtual_forwards.cf file with the following (or similar) contents:
user = postfixuser password = XXXXXXXXXX hosts = localhost dbname = postfix table = forwardings select_field = destination where_field = source
postfix check command. It should output anything that you might have done wrong in a config file.
To see all of your configs, type
postconf. To see how you differ from the defaults, try
postfix.service using systemd.
create a MySQL database
Create MySQL database called 'postfix', or something similar.
CREATE DATABASE postfix; USE postfix;
setup table structure
Import the following table structure.
CREATE TABLE `domains` ( `domain` varchar(50) NOT NULL default "", PRIMARY KEY (`domain`), UNIQUE KEY `domain` (`domain`) ); CREATE TABLE `forwardings` ( `source` varchar(80) NOT NULL default "", `destination` text NOT NULL, PRIMARY KEY (`source`) ); CREATE TABLE `users` ( `email` varchar(80) NOT NULL default "", `password` varchar(20) NOT NULL default "", `quota` varchar(20) NOT NULL default '20971520', `domain` varchar(255) NOT NULL default "", UNIQUE KEY `email` (`email`) );
create a MySQL user
Add a user for Postfix to use. Something like "postfixuser".
Give permissions for Postfix user to the table. This user should be listed in the
The official reference manual has a detailed guide on user management and server administration in general.
The following is just an example for creation of 'postfixuser' with password 'XXXXXXXXXX'. Note that the GRANT statements need to be executed after creating the tables in the next step.
CREATE USER 'postfixuser' IDENTIFIED BY 'XXXXXXXXXX'; GRANT SELECT, INSERT, UPDATE, DELETE ON domains TO postfixuser; GRANT SELECT, INSERT, UPDATE, DELETE ON forwardings TO postfixuser; GRANT SELECT, INSERT, UPDATE, DELETE ON users TO postfixuser;
add a domain
INSERT INTO `domains` VALUES ('virtualdomain.tld');
add a user
INSERT INTO `users` VALUES ('firstname.lastname@example.org', 'secret', '20971520', 'virtualdomain.tld');
The above creates the user and sets a password as secret.
This will allow you to use encrypted passwords
INSERT INTO `users` VALUES ('email@example.com', ENCRYPT('secret'), '20971520', 'virtualdomain.tld');
Start Postfix service. Now lets see if Postfix is going to deliver mail for our test user.
telnet servername 25 ehlo testmail.org mail from:<firstname.lastname@example.org> rcpt to:<email@example.com> data This is a test email. . quit
451 4.3.0 <firstname.lastname@example.org>:Temporary lookup failure
Maybe you have entered the wrong user/password for MySQL or the MySQL socket is not in the right place.
550 5.1.1 <email@example.com>: Recipient address rejected: User unknown in virtual mailbox table.
Double check content of mysql_virtual_mailboxes.cf and check the main.cf for mydestination
See that you have received a email
$ find /home/vmailer.
You should see something like the following:
/firstname.lastname@example.org /email@example.com/tmp /firstname.lastname@example.org/cur /email@example.com/new /firstname.lastname@example.org/new/1102974226.2704_0.bonk.testmail.org
The key is the last entry. This is an actual email, if you see that, it is working.
Configure Courier IMAP
We set the listen address to LOCAL ONLY. No outside connections.
Remove all the modules from the authmodulelist line except for authmysql like so:
Replace the entire file with the following:
MYSQL_SERVER localhost MYSQL_USERNAME postfixuser MYSQL_PASSWORD secret MYSQL_SOCKET /run/mysqld/mysqld.sock MYSQL_DATABASE postfix # MYSQL_NAME_FIELD name MYSQL_USER_TABLE users MYSQL_CLEAR_PWFIELD password MYSQL_UID_FIELD '5003' ##note, this is the uid that we set in /etc/postfix/main.cf MYSQL_GID_FIELD '5003' ##note, this is the gid that we set in /etc/postfix/main.cf MYSQL_LOGIN_FIELD email MYSQL_HOME_FIELD "/home/vmailer" MYSQL_MAILDIR_FIELD concat(domain,'/',email,'/') MYSQL_QUOTA_FIELD quota
Where secret is the MySQL password for the user postfixuser. If you are using encrypted passwords by using MySQL's encrypt function. Use "MYSQL_CRYPT_PWFIELD columnname" instead of "MYSQL_CLEAR_PWFIELD columnname".
For an alternative directory structure, you could also use this setting for MAILDIR_FIELD:
In this case, courier will use a directory like
Fam and rpcbind
Courier-imap for arch comes compiled with FAM. This means portmap is also required. What used to be portmap is nowadays called rpcbind.
local_only = true idle_timeout = 0
Make sure the two above values are set. Then start and enable the daemon rpcbind.
courier-imapd.service using systemd.
Lets see if courier is working:
telnet localhost imap Trying 127.0.0.1... Connected to localhost.localdomain. Escape character is '^]'. * OK [[CAPABILITY IMAP4rev1 ... ]] Courier-IMAP ready. A LOGIN "email@example.com" "password" A OK LOGIN Ok. B SELECT "Inbox" * FLAGS (\Draft \Answered ... \Recent) * OK [[PERMANENTFLAGS (\Draft \Answered ... \Seen)]] Limited * 8 EXISTS * 5 RECENT * OK [[UIDVALIDITY 1026858715]] Ok B OK [[READ-WRITE]] Ok Z LOGOUT * BYE Courier-IMAP server shutting down Z OK LOGOUT completed Connection closed by foreign host.
Create secure http site (https)
We are going to create a secure http site. This is so that people can login with plain text passwords, and not have to worry about the passwords getting sniffed (or worry less).
Add appropriate information. Here is an example section:
<VirtualHost _default_:443> # General setup for the virtual host DocumentRoot "/home/httpd/site.virtual/virtualdomain.tld/html" ServerName virtualdomain.tld:443 ServerAdmin noemailonthisbox@localhost <Directory "/home/httpd/site.virtual/virtualdomain.tld/html"> Options -Indexes +FollowSymLinks AllowOverride Options Indexes AuthConfig Order allow,deny Allow from all </Directory>
Include httpd-ssl.conf in httpd.conf
Simply uncomment this line in your httpd.conf:
Create the directory structure
Now, create the directory you specified in the ssl.conf file.
$ mkdir -p /home/httpd/site.virtual/virtualdomain.tld/html
Generate a certificate
Follow the instructions here: LAMP#SSL
restart Apache and test
Make sure that https is now working, and that you can get to the secure site.
put Squirrelmail in the directory you created
Either extract squirrelmail, or move it from where the arch package puts it, into the directory you created for the secure http site.
run Squirrelmail config utility
cd squirrelmaildir/config perl conf.pl
Make sure you select 'D', then type in courier and hit enter. Make sure your other options are correct as well. Note: If you use php with safe mode on, make sure that the data dir is owned by the same owner as all the files in the squirrelmail directory. With safe mode off, simply follow the squirrelmail setup directions.
test the Squirrelmail setup
Point your browser to squirrelmail/src/configtest.php. Should you get an error on directory location, make sure php.ini has been set to allow access to them (open_basedir directive).
Log in with the test account. You will need to login with the form of: username: firstname.lastname@example.org password: secret
Try sending email to non-existent local accounts. You should get an immediate bounce back. Try sending email to external good email accounts, as well as non-existent ones. Just general testing stuff. If everything works fine, then you can add other accounts to the MySQL database, and away you go!
If you received an error similar to:
Warning: file_exists() [function.file-exists]: open_basedir restriction in effect. File(/var/lib/squirrelmail/data) is not within the allowed path(s): \ (/srv/http/:/home/:/tmp/:/usr/share/pear/) in /home/httpd/site.virtual/virtualdomain.tld/html/squirrelmail/src/configtest.php on line 303
/etc/httpd/httpd.conf, and in the section:
php_admin_value open_basedir /home/httpd/site.virtual/virtualdomain.tld/html:/var/lib/squirrelmail/
If you get an error similar to:
Unknown user or password incorrect.
You may have to create your user directories within vmailer like so:
$ mkdir -p /home/vmailer/mydomain.com/username $ mkdir /home/vmailer/mydomain.com/username/cur $ mkdir /home/vmailer/mydomain.com/username/new $ mkdir /home/vmailer/mydomain.com/username/tmp $ chmod -R 750 /home/vmailer $ chown -R vmailer.vmail /home/vmailer
where mydomain.com/username is the domain/username given within MySQL.