UbuntuHelp:PostfixCompleteVirtualMailSystemHowto
来自Ubuntu中文
目录
- 1 Abstract
- 2 System Overview
- 3 How Postfix Mappings Work?
- 4 How Postfix Virtual Domains Work?
- 5 Installing a Ubuntu Server System
- 6 DNS Setup
- 7 Package Installation and Configuration
- 8 Postfix Base Server Installation
- 9 Installing Packages for Client Access and Authentication
- 10 Installing package for SMTP authentication
- 11 Setting MySQL Backend
- 12 Setting Postfix MySQL Maps
- 13 Configuring Postfix with MySQL maps
- 14 Enhanced Mail Services
- 15 Anti-Spam Configuration
- 16 Anti-Virus Configuration
- 17 Log Analyzer
- 18 Wrapping it Up
- 19 Final Changes and Troubleshooting
Abstract
There are many howtos in the Internet about setting up mail servers and various people has various choice of MTAs. Some like, Qmail, while some like Postfix or Exim. I have been using Qmail for a long time and it is an excellent MTA. The way the Qmail is licensed and distributed that there are no binary packages so that users can easily setup with their favorite distribution, and installing basic Qmail setup even is not that difficult but users need applied various patches and tweaks etc to get a complete setup done. With all these issues Qmail is the preferred choice of many geeks, since it won't give you head ache once up and running. The drawback is that this system is difficult to upgrade since users need to compile the source code and install.
The decision behind this guide is to use Postfix,an equally secure and fast MTA like Qmail, it is easy to configure and setup a Basic System in any Linux distribution. Postfix has many add-ons and support Maildir format, PostgreSQL and MySQL backend for storing and managing virtual domains very easily. This setup will be a complete virtual mail domain systems , with anti-virus and spam filtering for ISPs , hosting companies, and individual corporations who wish to use Ubuntu Linux as there preferred server platform.
System Overview
It is important to know how our system works before going to install. A virtual mail system needs to be able to handle email for numerous domains with multiple users over a variety of interfaces. When you handle multiple domains within the same mail system it presents you some management issues. We have to answer these issues using our technology. Assume ,for example you may have following questions to answer.
- What will you do if you have two users which require same username for different domains?
- If you are providing imap access and smtp-auth, how do combine the various authentication daemons into a single system?
- How do you provide security for the numerous components that comprise the system?
- What we can do, if users are asking their own spam filtering policies.
- Individual domain administrators are asking a web-based interface to manage their mail domains
- How do you setup a web-based management system for Postfix?
- Each user needs a web-base interface to change his mail account's password
- How you are going backup user account database and disaster recovery?.
- Utilizing ssl for transport layer security
- Handle mailing lists for any domain
How do you manage all these issues together?
Don't panic, I will answer all these questions one by one. Be happy and continue to read this howto.
What You Get
- Web based system administration
- Unlimited number of domains
- Virtual mail users without the need for shell accounts
- Domain specific user names
- Mailbox quotas
- Web access to email accounts
- Web base interface to change user passwords
- IMAP and POP3 support
- Auto responders
- SMTP Authentication for secure relaying
- SSL for transport layer security
- Strong SPAM filtering
- Anti-Virus filtering
- Log Analysis
Packages Required
The following packages are need to implement our system and most of these packages are in APT repositories. In our installation section you will learn how to install and configure each.
- Webmin
- Postfix
- MySQL
- Apache
- PHP
- Postfixadmin
- Courier-IMAP
- Courier-POP3
- Courier-authlib
- Cyrus-SASL
- Ispell
- Squirrelmail
- Awstats
- Amavisd-new
- Spamassassin
- MailZu
- Razor
- DCC
- Pyzor
- SQLgrey
- Sgwi
- Clamav
The Big Picture
The following figure shows the big picture of our setup. If you look at it carefully the figure itself is self explanatory.
In our setup:
- Postfix Mail Transfer Agent receives emails via the SMTP protocol and delivers them to different places on your hard disk.
- MySQL database server stores the information to control the behavior of postfix. It knows about users, domains, email forwarding and passwords.
- Courier is a standalone mail server just like Postfix but we just use its POP3/IMAP server component to let users access the mailboxes.
- SASL, the Cyrus library is using to authenticate your users who are dialed in at another ISP while they are on the road they get an IP address outside of your network. Your mail server however only trusts local IP addresses. The SASL ,Simple Authentication and Security Layer, adds authentication to SMTP and makes your mail server trust them.
How Postfix Mappings Work?
It is very important to understand how Postfix mapping works. Heart of our system is Postfix mapping. Let's discuss it here. Don't skip this section.
The generic literal meaning of mapping is assign one value to another. What we have to map in Postfix is email user accounts or email address. One example is /etc/aliases
, the local aliases or local system users mapping file used by Postfix. The syntax of this file is:
postmaster: root
This makes all the mails which are coming to [email protected]
are redirected to [email protected]
. We can divide the above syntax to Left Hand Side LHS and Right Hand Side RHS. This RHS and LHS are common abbreviations which we usually used in mappings. The following table will make this idea even more clear.
LHS | RHS |
postmaster: | root |
Usually we do not use colon(:) in LHS for Postfix and this has been done for backward compatibility with historical reasons. The local alias file is a special file that is compiled with newaliases command but not with usual Postfix mapping command postmap |
With a basic default Postfix installation we use text file for mappings. We write the mappings into this file and then convert it into a hash file using postmap command so Postfix can look up items quickly. For example, assume that we need to map our virtual mailboxes in a file called /etc/Postfix/virtual_mailboxes
. The syntax of this file look like:
[email protected] sigiri [email protected] kala
You may have noticed that we don't have colon(:) in the LHS of the mappings file
Then you need to run:
postmap /etc/postfix/virtual_mailboxes
You can access this mappings in the Postfix configuration file by including the following line:
virtual_mailbox_maps=hash:/etc/postfix/virtual_mailboxes
In our setup, we will replace this text mapping files with MySQL tables. Our intention is to make data handling lot more flexible, robust, and scalable. Since database tables can and usually contain more than just two columns you will need to tell Postfix which database column is meant to be the LHS and which is the RHS. This is accomplished by creating a configuration file which will look something like this:
user = postfix password = YJiNLQtubgnOE hosts = 127.0.0.1 dbname = postfix table = mailbox select_field = maildir where_field = username
For the purposes of this discussion, lets assume this is saved in a file called /etc/postfix/mysql_virtual_mailbox_maps.cf
. You would then be able to use this mapping in postfix using the following entry in main.cf
file.
virtual_mailbox_maps = mysql:/usr/local/etc/postfix/mysql_virtual_mailbox_maps.cf
The fields in this configuration file are the user that needs to connect to the MySQL database, password of that MySQL user, dbname, the name of the MySQL database, table ,the name of the table in MySQL database and hosts, the name of the server that MySQL runs on.
Postfix uses the this configuration file as a guide on how to use the database table as a mapping similar to the mapping file with two fields described above. The LHS of the mapping is defined as where_field
and the RHS is defined as select_field
. In this example we will map the maildir
column to the username
column. Using the configuation, Postfix constructs a SQL query something like select maildir from postfix.mailbox where username='johndoe' to lookup the maildir for a given username. The following table breaks this distiction out:
LHS | RHS |
where_field | select_field |
username | maildir |
How Postfix Virtual Domains Work?
Understanding how virtual domains work is very important to understand how our virtual mail setup works.
There are two types of domains in Postfix.
- Local domains: All domains which are listed as mydestination are treated as local domains by Postfix. Emails for local domains are delivered to system users which are listed in
/etc/passwd
file and these mails are spooled in/var/mail
directory.
- Virtual domains: In addition to the local domains Postfix can deliver mails for virtual domains. Not like local domains, Postfix will let us to handle virtual domains in a very flexible manner. The good thing is with virtual domains is that we do not need system account in
/etc/passwd
for each and every mail account. This provides us a way to handle thousands of mail accounts very easily in our mail server system. The mapping which we discussed above is used to handle mail account information. You can use MySQL, PostgreSQL , or LDAP for the user account management. In our setup we use MySQL backend to manage user accounts of virtual domains.
Postfix handles virtual domains as two different categories and need to understand how they work.
- Virtual alias domains: These domains are used to forward or alias mails from one email address to another email address. Such domains can be used receive mailboxes and store on your hard disk. You do not necessarily need to use virtual alias domains in your setup. Instead we can user virtual_alias_maps even if the domains are not listed as virtual alias domains. The virtual_alias_maps is a general-purpose redirection mapping that works for everything that passes your system including local domains.
- Virtual mailbox domains: Postfix uses these domains to receive mails for users under the domains and store them in the mailboxes on the hard disk. This is parameter which will simply tell Postfix to receive the mails on behalf of the domain and store them in each user's mailbox. The virtual_mailbox_maps mapping is used by Postfix to determine the location of the mailbox on your hard disk. Please remember that you can still use the virtual_alias_maps mapping to forward email to other mailboxes or external email addresses so not every user on that domain must actually have a mailbox but can also just have the email forwarded somewhere else.
It is important to understand that a domain is either a virtual alias domain or a virtual mailbox domain or a local domain. If you make a domain a virtual alias domain you will not be able to receive email for that domain on your server. On the contrary you can use the virtual_alias_maps to forward?action=AttachFile&do=get&target=alias email for both types of domain. So the virtual mailbox domains are generally the more flexible to use. |
A domain can either be virtual or local and you can not use one domain in the both of these roles. Please never both. So if you decide you want your default domain be a virtual domain then remove it from the mydestination definition. Just leave it blank or set it to mydestination=localhost. Email addresses like root@localhost would then be delivered to the local root user. |
Installing a Ubuntu Server System
In this howto I assume that you already know how to setup a Ubuntu server system. I would suggest you to do a Ubuntu server installation without a GUI. If you want to know more about installation look here
DNS Setup
This how to assumes that you already have at least one valid registered domain with an MX record setup for that domain. Setting up a BIND DNS server can be learned here
Package Installation and Configuration
You will to have install and configure all packages which I have mentioned in the "Package Required" section. Let's deal with one by one.
Postfix Base Server Installation
Here we install Postfix and other packages which Postfix requires connect with a MySQL backend.
Installing Postfix
When you install Postfix I would suggest to select "Internet Site" option.
To install Postfix, you need to install the postfix
package. For Postfix documentation, you need the postfix-doc
package.
Installing MySQL map support for Postfix
We need to add MySQL mapping support for Postfix. Hope that you have already read How Postfix Mappings Work? section in this howto.
To install postfix-mysql, install the postfix-mysql
package.
To install MySQL client program, install the mysql-client
package.
To install MySQL server, install the mysql-server
package.
Installing Packages for Client Access and Authentication
We will need to offer our user IMAP/POP3 access. Our setup will offer those using the following packages.
To provide client authentication, install the courier-authdaemon
package.
To add MySQL support for courier-authdaemon, install the courier-authmysql
package.
To provide unencrypted POP3 access, install the courier-pop
package.
To provide SSL-encrypted POP3 access, install the courier-pop-ssl
package.
To provide unencrypted IMAP access, install the courier-imap
package.
To provide SSL-encrypted IMAP access , install the courier-imap-ssl
package.
Installing package for SMTP authentication
Our system will allow road-warriors to send email through our server using authenticated SMTP. This will basically stop unauthorized relaying through our mail server. Not only we are authenticating our user's when they are retrieving mails but also we authenticate them when they are sending mails as well.
To provide encrypted authenticated SMTP, install the postfix-tls
package.
This may have already installed with postfix. If so,leave it.
To install Cyrus SASL library, install the libsasl2
package.
To add authentication mechanisms for the SASL library, install the libsasl2-modules
package.
To add MySQL support authentication mechanisms with the SASL library, install the libsasl2-modules-sql
package.
To create certificates, install the openssl
package.
Setting MySQL Backend
Now that we have installed packages required to prepare a MySQL backend for Postfix. In this section we will configure MySQL database for Postfix.
Setting MySQL root Password
Please note that MySQL root is different from Linux root account. It is the account which which users can use to get administrative previlege with MySQL database sever. Initial installation of MySQL has no password fro root account. If you have not setup a password for MySQL root yet, this is the time for you to do so. There are few ways to do the same and I will present two of them here. Please user either one of them.
To set MySQL root in the comand prompt:
sudo mysqladmin -u root password rootpassword
or you can use the following steps to do the same
Type in a terminal
mysql -u root
Then in the mysql prompt type:
mysql>SET PASSWORD FOR 'root'@'localhost' = PASSWORD('rootpasswotd'); mysql>\q
Don't forget set a good password rootpassword
Setting MySQL Database for Impatient Users
The schema is based on the postfixadmin MySQL schema. If you are impatient you can driectly create the tables using following steps.
vi postfixadmin-mysql.sql
Then copy and paste the following script to the above file and save it. Replace postfixpassword on the INSERT INTO user
line with a password of your choosing for the postfix user. Do the same for the postfixadmin password.
To create the database, type in a terminal.
mysql -u root -p < postfixadmin-mysql.sql
#------------------------------------Start copy------------------------------------- USE mysql; INSERT INTO user (Host, User, Password) VALUES ('localhost','postfix',password('postfixpassword')); INSERT INTO db (Host, Db, User, Select_priv) VALUES ('localhost','postfix','postfix','Y'); INSERT INTO user (Host, User, Password) VALUES ('localhost','postfixadmin',password('postfixadmin')); INSERT INTO db (Host, Db, User, Select_priv, Insert_priv, Update_priv, Delete_priv) VALUES ('localhost', 'postfix', 'postfixadmin', 'Y', 'Y', 'Y', 'Y'); FLUSH PRIVILEGES; GRANT USAGE ON postfix.* TO postfix@localhost; GRANT SELECT, INSERT, DELETE, UPDATE ON postfix.* TO postfix@localhost; GRANT USAGE ON postfix.* TO postfixadmin@localhost; GRANT SELECT, INSERT, DELETE, UPDATE ON postfix.* TO postfixadmin@localhost; CREATE DATABASE postfix; USE postfix; CREATE TABLE admin ( username varchar(255) NOT NULL default '', password varchar(255) NOT NULL default '', created datetime NOT NULL default '0000-00-00 00:00:00', modified datetime NOT NULL default '0000-00-00 00:00:00', active tinyint(1) NOT NULL default '1', PRIMARY KEY (username), KEY username (username) ) TYPE=MyISAM COMMENT='Postfix Admin - Virtual Admins'; CREATE TABLE alias ( address varchar(255) NOT NULL default '', goto text NOT NULL, domain varchar(255) NOT NULL default '', created datetime NOT NULL default '0000-00-00 00:00:00', modified datetime NOT NULL default '0000-00-00 00:00:00', active tinyint(1) NOT NULL default '1', PRIMARY KEY (address), KEY address (address) ) TYPE=MyISAM COMMENT='Postfix Admin - Virtual Aliases'; CREATE TABLE domain ( domain varchar(255) NOT NULL default '', description varchar(255) NOT NULL default '', aliases int(10) NOT NULL default '0', mailboxes int(10) NOT NULL default '0', maxquota int(10) NOT NULL default '0', transport varchar(255) default NULL, backupmx tinyint(1) NOT NULL default '0', created datetime NOT NULL default '0000-00-00 00:00:00', modified datetime NOT NULL default '0000-00-00 00:00:00', active tinyint(1) NOT NULL default '1', PRIMARY KEY (domain), KEY domain (domain) ) TYPE=MyISAM COMMENT='Postfix Admin - Virtual Domains'; CREATE TABLE domain_admins ( username varchar(255) NOT NULL default '', domain varchar(255) NOT NULL default '', created datetime NOT NULL default '0000-00-00 00:00:00', active tinyint(1) NOT NULL default '1', KEY username (username) ) TYPE=MyISAM COMMENT='Postfix Admin - Domain Admins'; CREATE TABLE log ( timestamp datetime NOT NULL default '0000-00-00 00:00:00', username varchar(255) NOT NULL default '', domain varchar(255) NOT NULL default '', action varchar(255) NOT NULL default '', data varchar(255) NOT NULL default '', KEY timestamp (timestamp) ) TYPE=MyISAM COMMENT='Postfix Admin - Log'; CREATE TABLE mailbox ( username varchar(255) NOT NULL default '', password varchar(255) NOT NULL default '', name varchar(255) NOT NULL default '', maildir varchar(255) NOT NULL default '', quota int(10) NOT NULL default '0', domain varchar(255) NOT NULL default '', created datetime NOT NULL default '0000-00-00 00:00:00', modified datetime NOT NULL default '0000-00-00 00:00:00', active tinyint(1) NOT NULL default '1', PRIMARY KEY (username), KEY username (username) ) TYPE=MyISAM COMMENT='Postfix Admin - Virtual Mailboxes'; CREATE TABLE vacation ( email varchar(255) NOT NULL default '', subject varchar(255) NOT NULL default '', body text NOT NULL, cache text NOT NULL, domain varchar(255) NOT NULL default '', created datetime NOT NULL default '0000-00-00 00:00:00', active tinyint(1) NOT NULL default '1', PRIMARY KEY (email), KEY email (email) ) TYPE=MyISAM COMMENT='Postfix Admin - Virtual Vacation';
Step by Step Database Setup
The users who are wish to setup database step by step can use the following steps and understand what table is using what purpose.
Setting up Database, Users, and Privileges
Connect to MySQL database as root
mysql -u root -p
Then type the following sql commands.
To use MySQL user database:
USE mysql;
To create Postfix user & set password (replace postfixpassword with a password of your choosing):
mysql>INSERT INTO user (Host, User, Password) VALUES ('localhost','postfix',password('postfixpassword')); mysql>INSERT INTO db (Host, Db, User, Select_priv) VALUES ('localhost','postfix','postfix','Y');
To create Postfix Admin user & set password:
mysql>INSERT INTO user (Host, User, Password) VALUES ('localhost','postfixadmin',password('postfixadmin')); mysql>INSERT INTO db (Host, Db, User, Select_priv, Insert_priv, Update_priv, Delete_priv) VALUES ('localhost', 'postfix', 'postfixadmin', 'Y', 'Y', 'Y', 'Y'); mysql>FLUSH PRIVILEGES;
To Add Privileges for users:
mysql>GRANT USAGE ON postfix.* TO postfix@localhost; mysql>GRANT SELECT, INSERT, DELETE, UPDATE ON postfix.* TO postfix@localhost; mysql>GRANT USAGE ON postfix.* TO postfixadmin@localhost; mysql>GRANT SELECT, INSERT, DELETE, UPDATE ON postfix.* TO postfixadmin@localhost;
To create and use the database:
mysql>CREATE DATABASE postfix; mysql>USE postfix;
Create the Table Admin
This table is used create the administrators for our virtual mail system. The admin user will be able create, modify, and delete virtadomain administrators, mailboxes and other administrative tasks in the mail system. Postfix is not using this table.
Copy and paste the sql statement to your mysql> prompt.
CREATE TABLE admin ( username varchar(255) NOT NULL default '', password varchar(255) NOT NULL default '', created datetime NOT NULL default '0000-00-00 00:00:00', modified datetime NOT NULL default '0000-00-00 00:00:00', active tinyint(1) NOT NULL default '1', PRIMARY KEY (username), KEY username (username) ) TYPE=MyISAM COMMENT='Postfix Admin - Virtual Admins';
Create the Alias table
Postfix is using the "address" and "goto" column. Courier is not using this table.
This table can be used for virtual .forward files. This table is nothing more than ?action=AttachFile&do=get&target=etc%2Faliases%3C%2Fnowiki%3E%3C%2Fcode%3E%27%27%27 that you will find on any *nix OS. Multiple destination email addresses need to be separated by a "," (comma).
|}
Following is the table structure for table alias. Copy and paste the sql statement to your '''mysql>''' prompt
<pre><nowiki>
CREATE TABLE alias (
address varchar(255) NOT NULL default '',
goto text NOT NULL,
domain varchar(255) NOT NULL default '',
created datetime NOT NULL default '0000-00-00 00:00:00',
modified datetime NOT NULL default '0000-00-00 00:00:00',
active tinyint(1) NOT NULL default '1',
PRIMARY KEY (address),
KEY address (address)
) TYPE=MyISAM COMMENT='Postfix Admin - Virtual Aliases';
</pre>
Create the Domain tablePostfix is using the "domain" and "description" column. Courier is not using this table. Copy and paste the sql statement to your mysql> prompt CREATE TABLE domain ( domain varchar(255) NOT NULL default '', description varchar(255) NOT NULL default '', aliases int(10) NOT NULL default '0', mailboxes int(10) NOT NULL default '0', maxquota int(10) NOT NULL default '0', transport varchar(255) default NULL, backupmx tinyint(1) NOT NULL default '0', created datetime NOT NULL default '0000-00-00 00:00:00', modified datetime NOT NULL default '0000-00-00 00:00:00', active tinyint(1) NOT NULL default '1', PRIMARY KEY (domain), KEY domain (domain) ) TYPE=MyISAM COMMENT='Postfix Admin - Virtual Domains'; Create the Domain Admin TableTable structure for table domain_admins. This table is used to create individual administrators for each virtual domain. Postfix or Courier is not using this table. Copy and paste the sql statement to your mysql> prompt. CREATE TABLE domain_admins ( username varchar(255) NOT NULL default '', domain varchar(255) NOT NULL default '', created datetime NOT NULL default '0000-00-00 00:00:00', active tinyint(1) NOT NULL default '1', KEY username (username) ) TYPE=MyISAM COMMENT='Postfix Admin - Domain Admins'; Create the Mailbox TablePostfix is using the "username" and "maildir" column while Courier is using the "username", "password", "name" and "maildir" column. Copy and paste the sql statement to your mysql> prompt. CREATE TABLE mailbox ( username varchar(255) NOT NULL default '', password varchar(255) NOT NULL default '', name varchar(255) NOT NULL default '', maildir varchar(255) NOT NULL default '', quota int(10) NOT NULL default '0', domain varchar(255) NOT NULL default '', created datetime NOT NULL default '0000-00-00 00:00:00', modified datetime NOT NULL default '0000-00-00 00:00:00', active tinyint(1) NOT NULL default '1', PRIMARY KEY (username), KEY username (username) ) TYPE=MyISAM COMMENT='Postfix Admin - Virtual Mailboxes'; Create the Log TablePostfix or Courier is not using this table. Instead this table is used to log the activities of domain administrators and mailbox users. Copy and paste the sql statement to your mysql> prompt. CREATE TABLE log ( timestamp datetime NOT NULL default '0000-00-00 00:00:00', username varchar(255) NOT NULL default '', domain varchar(255) NOT NULL default '', action varchar(255) NOT NULL default '', data varchar(255) NOT NULL default '', KEY timestamp (timestamp) ) TYPE=MyISAM COMMENT='Postfix Admin - Log'; Create the Vacation TableVirual Vacation is done with a local shell account that can receive email. The email is then handled by a Perl script which sends the Vacation message back to the sender. Copy and paste the sql statement to your mysql> prompt. CREATE TABLE vacation ( email varchar(255) NOT NULL default '', subject varchar(255) NOT NULL default '', body text NOT NULL, cache text NOT NULL, domain varchar(255) NOT NULL default '', created datetime NOT NULL default '0000-00-00 00:00:00', active tinyint(1) NOT NULL default '1', PRIMARY KEY (email), KEY email (email) ) TYPE=MyISAM COMMENT='Postfix Admin - Virtual Vacation'; Setting Postfix MySQL MapsAs specified earlier in this document you need to tell Postfix where the control information is stored in the database. You need to create the following four text files in /etc/postfix for that reason. Note that in the files we create below, we specify <code>127.0.0.1 for the
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