Postfix

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 (Template:Filename). 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.

For a local mail delivery guide guide, see: Local Mail Delivery with Postfix.

Required packages

• postfix (compiled for mysql support)
• courier-imap
• squirrelmail
• mysql
• apache
• ssl

If you have trouble finding a package specific to this How-To, try the resources link at the bottom.

Postfix Installation

Step 1: Install Postfix

Postfix with MySQL enabled is required for this HOW-TO. So we will install the package called postfix which can be found in the official repositories.

Step 2: Check /etc/passwd, /etc/group

Make sure that the following shows up in /etc/passwd:

postfix:x:73:73::/var/spool/postfix:/bin/false

Make sure that the following shows up in /etc/group:

postdrop:x:75:
postfix:x:73:

Note: Postfix can be made to run in a chroot. This document does not currently cover this and might be added later.

Postfix Configuration

Step 1: Ensure DNS setup

For mail delivery on the internet, your dns must be correct. An MX record should point to the mail host. It should be noted that some mail servers will not deliver mail to you if your MX record points to a CNAME. For best results, always point an MX record to an A record definition. More info about DNS and records is beyond the scope of this document.

Step 2: /etc/postfix/master.cf

This is the Pipeline configuration file, in which you can put your new pipes e.g. to check for Spam!

Step 3: /etc/postfix/main.cf

Step 3.1 myhostname

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

Step 3.2 mydomain

this is usually the value of myhostname, minus the first part. If your domain is wonky, then just set it manually.

mydomain = nospam.net

Step 3.3 myorigin

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

Step 3.4 mydestination

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

Step 3.5 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

Step 3.6 relaydomains

This controls the destinations that postfix will relay TO. The default value is $mydestination. This should be fine for now.

relay_domains = $mydestination

Step 3.7 home_mailbox

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/

Step 3.8 virtual_mail

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.

Step 3.9 Default message & 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

Step 4. /etc/postfix/aliases

We need to map some aliases to real accounts. The default setup by arch looks pretty good here. =D 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.

root: cactus

Once you have finished editing /etc/postfix/aliases you must run the postalias command.

postalias /etc/postfix/aliases

Step 5. /etc/postfix/virtual_alias

Create /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:           cactus@virtualdomain.tld

Then run the postalias command on it.

postalias /etc/postfix/virtual_alias

Step 6. mysql_virtual_domains.cf

Create the /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

Step 7. mysql_virtual_mailboxes.cf

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

Step 8. mysql_virtual_forwards.cf

Create the /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

Step 9. postfix check

Run the 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 postconf -n

Step 10. /etc/rc.conf

Add postfix to the list of daemons. Put it near the right side, after iptables and network. Put it after mysqld, as we are going to be using mysql for some of the virtual domain information storage. It is also best to put it before httpd, as it might be possible, however unlikely, for a webmail user to try something before postfix has fully started.

DAEMONS=(syslog-ng hotplug !pcmcia iptables network netfs crond sshd mysqld postfix httpd)

Step 11. newuser

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

note that 5003 is the gid specified in the postfix main.cf file. note that 5003 is the uid specified in the postfix main.cf file.

Mysql configuration

Step 1. Create a mysql Database

Create mysql database called 'postfix', or something similar.

CREATE DATABASE postfix;
USE postfix;

Step 2. 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 /etc/postfix/mysqlvirtualdomains.cf file.

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;

Step 3. 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`)
);

Step 4. Add a domain.

INSERT INTO `domains` VALUES ('virtualdomain.tld');

Step 5. Add a user.

INSERT INTO `users` VALUES ('cactus@virtualdomain.tld', '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 ('cactus@virtualdomain.tld', ENCRYPT('secret'), 
'20971520', 'virtualdomain.tld');

Test Postfix

Step 1: Start postfix

/etc/rc.d/postfix start

Step 1: Test postfix

Lets see if postfix is going to deliver mail for our test user.

telnet servername 25
ehlo testmail.org
mail from:<test@testmail.org>
rcpt to:<cactus@virtualdomain.tld>
data
This is a test email.

.
quit

now type the following:

find /home/vmailer

you should see something like the following:

/home/vmailer/virtualdomain.tld/cactus@virtualdomain.tld
/home/vmailer/virtualdomain.tld/cactus@virtualdomain.tld/tmp
/home/vmailer/virtualdomain.tld/cactus@virtualdomain.tld/cur
/home/vmailer/virtualdomain.tld/cactus@virtualdomain.tld/new
/home/vmailer/virtualdomain.tld/cactus@virtualdomain.tld/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.

Courier IMAP Installation

Step 1: Install Courier IMAP

pacman -S courier-imap courier-imap-mysql

Configure Courier IMAP

Step 1: /etc/courier-imap/imapd

ADDRESS=127.0.0.1

We set the listen address to LOCAL ONLY. No outside connections.

Step 2: /etc/authlib/authdaemonrc

authmodulelist="authmysql"

Step 3: /etc/authlib/authmysqlrc

MYSQL_SERVER            localhost
MYSQL_USERNAME          postfixuser
MYSQL_PASSWORD          secret
MYSQL_SOCKET            /var/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

If your using encrypted passwords by using MySQL's encrypt function. Use "MYSQL_CRYPT_PWFIELD columnname" instead of "MYSQL_CLEAR_PWFIELD columnname".

Step 6: /etc/conf.d/courier-imap

First start the courier-imap daemon then stop it right away. I do not know exactly what this does (if anything.lol), but I have attempted the following step without having fulfilled that precondition and it borked on me. shrug A quick

/etc/rc.d/authdaemond start
/etc/rc.d/courier-imap start
/etc/rc.d/courier-imap stop
/etc/rc.d/authdaemond stop

should be enough. Now, remove the pop3d listings from courier-imap. We are only using the imap facility. Since the daemon is local only (localhost), we do not need the ssl imapd server either. /etc/conf.d/courier-imap

CI_DAEMONS="imapd"
#CI_DAEMONS="imapd pop3d imapd-ssl pop3d-ssl"

Step 7: Add courier-imap to rc.conf

DAEMONS=(syslog-ng hotplug !pcmcia iptables network netfs crond sshd mysqld postfix authdaemond courier-imap httpd)

Again, make sure to add courier after postfix, after mysqld and after postfix, yet before httpd.

Step 8: 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. If rpcbind is not already installed:

pacman -S rpcbind

Now edit /etc/fam/fam.conf

local_only = true
idle_timeout = 0

Make sure the two above values are set.

Now add rpcbind and fam to the daemons list in /etc/rc.conf

DAEMONS=(syslog-ng hotplug !pcmcia iptables network netfs crond sshd mysqld postfix rpcbind fam
courier-imap httpd)

Make sure that rpcbind starts after network, but before fam, and fam starts before courier. Now start them.

/etc/rc.d/rpcbind start
/etc/rc.d/fam start

Step 9: Start courier imap

/etc/rc.d/courier-imap start

check /var/log/mail.log for any errors.

Step 10: Test courier..

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 "cactus@virtualdomain.tld" "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.

Squirrelmail Installation

Step 1: Install Squirrelmail

Install the squirrelmail package which is found in the official repositories.

Configure Squirrelmail

Step 1: 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).

Step 1.1: Edit /etc/httpd/conf/extra/httpd-ssl.conf

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>

Step 1.15 Include httpd-ssl.conf in httpd.conf

Simply uncomment this line in your httpd.conf:

#Include conf/extra/httpd-ssl.conf

Step 1.2: Create the directory structure

Now, create the directory you specified in the ssl.conf file.

mkdir -p /home/httpd/site.virtual/virtualdomain.tld/html

Step 1.3: Generate a certificate

Follow the instructions here: LAMP#SSL

Step 1.4: Restart apache and test

Make sure that https is now working, and that you can get to the secure site.

Step 2: 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.

Step 3: 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.

Step 4: 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).

Step 5: Test squirrelmail

Log in with the test account. You will need to login with the form of: username: cactus@virtualdomain.tld 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!

Troubleshooting

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

then edit /etc/httpd/httpd.conf, and in the section <Directory "/home/httpd/site.virtual/virtualdomain.tld/html">, add php_admin_value open_basedir /home/httpd/site.virtual/virtualdomain.tld/html:/var/lib/squirrelmail/

See also

• Simple Virtual User Mail System
• Courier MTA
• SOHO Postfix

External links

• Out of Office for squirrelmail
• Postfix Ubuntu documentation
• A Simple Mailserver on Arch Linux