Linux mail server construction experiment
Preface
This article focuses on the construction process in the back. The principle and work flow of the mail service will be briefly introduced in the front. If there are any errors or omissions, you are welcome to correct and criticize, thank you.
Basic theory description
E-mail server is a general term for software and hardware facilities that handle mail exchanges, including e-mail programs, e-mail boxes, etc. It is an e-mail system based on E-mail service for users, and people can exchange e-mails by accessing the server. At the same time, mail has legal benefits and can provide proof, but instant messaging software cannot do this. Some companies build internal mail services for information security.
Common mail server
Sendmail、Qmail、Postfix、Zmailer、Exchange（MS）、Notes/Domino（IBM）
、Coremail、U-Mail、盈世。
Mail server composition
The email system consists of many parts, four of which are briefly introduced below.
MUA (Mail User Agent)
Refers to mail client programs such as Foxmail, Outlook, etc.
MTA (Mail Transfer Agent)
MTA (Mail Transfer Agent), MTA means "mail transfer agent", MTA is the software used on the mail host, it is also the main mail server. The main functions of MTA are as follows. It receives letters from external hosts and helps users send (send) letters. MTA will send letters to the destination MTA instead of the destination MUA. Common MTA software Postfix, Coremail, Sendmail, etc.
MDA (Mail Distribution Agent)
MDA (Mail Delivery Agent), the main function of "Mail Delivery Agent" is to place the letter received by the MTA into the mail file (inbox) under the local account according to the flow of the letter (where to send it), or Send the letter to the next MTA via the MTA. If the flow of mail is to the local machine, the function of this mail agent is not only to place the mail sent by the MTA into each user's inbox, it can also have mail filtering and other related functions, common MDA software : Maildrop
MRA (mail acquisition agent)
MRA (Mail Retrieval Agent) obtains their own emails for users. The “Mail Retrieval Agent” asks for services that enable MUA to obtain emails remotely, such as qpoper, cyrus-imap, courier-imap, dovecot, etc., in order to save emails. The format is compatible, and the mail delivery agent order MDA is often requested in the MRA order. The protocols used by MRA are POP3 and IMAP4. POP3 allows users to download emails from the server and read them offline. IMAP4 is used for those users who don't have foreign mailboxes, and has the ability to operate mailboxes remotely. IMAP4 allows multiple client machines to access a mailbox at the same time.
Protocol used
Sending protocol MUA》 MTA
SMTP: Simple Mail Transfer Protocol, TCP 25 port, use TCP 465 port for encryption
Receiving Agreement MUA》 MRA
POP3: The third version of the post office protocol, TCP port 110, use TCP 995 port when encrypting
IMAP4: the fourth version of Internet Message Access Protocol, TCP port 143, use TCP 993 port when encrypting
Experimental steps
The purpose of the experiment: master the basic mail service architecture.
Experiment preparation: one C6 standard test machine (firewall and selinux are closed)
Experimental planning: 192.168.10.14 (mail server)
192.168.10.15 (access test)
Experiment related installation package: mail service
ps: For standard virtual machine installation, please refer to the Centos6 installation guide in the network phase
One, configure DNS service
yum install -y bind
Edit the main configuration file
vim /etc/named.conf
Modified to accept all addresses
Edit zone file
vim /etc/named.rfc1912.zones
Configure forward and reverse analysis zones
zone "extmail.org." IN {
type master;
file "extmail.zheng";
allow-update {
none; };
};
zone "10.168.192.in-addr.arpa" IN {
type master;
file "extmail.fan";
allow-update {
none; };
};
Create parse file
cd /var/named/
cp -a named.localhost extmail.zheng
cp -a named.loopback extmail.fan
Forward file configuration
vim extmail.zheng
$TTL 1D
@ IN SOA extmail.org. rname.invalid. (
0 ; serial
1D ; refresh
1H ; retry
1W ; expire
3H ) ; minimum
NS dns.extmail.org.
MX 3 mail.extmail.org.
mail A 192.168.10.14
dns A 192.168.10.14
Reverse file parsing
vim extmail.fan
$TTL 1D
@ IN SOA extmail.org. rname.invalid. (
0 ; serial
1D ; refresh
1H ; retry
1W ; expire
3H ) ; minimum
NS dns.extmail.org.
MX 3 mail.extmail.org.
14 PTR dns.extmail.org.
14 PTR mail.extmail.org.
Start the service, set it to self-start after booting, and test whether the DNS configuration is successful.
service named start
chkconfig named on
echo "DNS1=192.168.10.14" >> /etc/sysconfig/network-scripts/ifcfg-eth0
service network restart
nslookup
The test passed, and both the forward analysis and reverse analysis were set successfully.
Two, configure MySQL service
yum install mysql mysql-server mailx httpd -y
Start the service and set it to start at boot
service mysqld start
chkconfig mysqld on
Set initial password
mysqladmin -uroot password 123
Connect to the database test
mysql -uroot -p123
The database is set up.
Three, configure the Apache service
yum -y install httpd lrzsz
Create mail service web file directory
mkdir /var/www/extsuite
Prepare the extmail installation image (download link above), create a mount directory, and mount the installation image.
mkdir /mnt/iso
mount -o loop EXTMAIL.iso /mnt/iso/
Copy all files in the mirror to the root directory
cd
cp -a /mnt/iso/* .
Unzip the file to the corresponding directory
tar -zxf extmail-1.2.tar.gz -C /var/www/extsuite/
tar -zxf extman-1.1.tar.gz -C /var/www/extsuite/
Simplify the directory name for easy access.
cd /var/www/extsuite/
mv extmail-1.2 extmail
mv extman-1.1 extman
Perform administrator configuration and generate encrypted passwords.
grub-md5-crypt
Replace the administrator password with the generated encrypted password.
vim init.sql
Restore the two database files to the database
mysql -uroot -p < extmail.sql
mysql -uroot -p < init.sql
Fourth, configure POSTFIX service
Copy the template file to the specified location
cp mysql_virtual_alias_maps.cf mysql_virtual_domains_maps.cf mysql_virtual_mailbox_maps.cf /etc/postfix/
Configure specified users
useradd -u 600 vmail
postconf -e inet_interfaces=all
postconf -e virtual_mailbox_base=/home/vmail
postconf -e virtual_uid_maps=static:600
postconf -e virtual_gid_maps=static:600
Configure the template file and start the service.
postconf -e virtual_alias_maps=mysql:/etc/postfix/mysql_virtual_alias_maps.cf
postconf -e virtual_mailbox_domains=mysql:/etc/postfix/mysql_virtual_domains_maps.cf
postconf -e virtual_mailbox_maps=mysql:/etc/postfix/mysql_virtual_mailbox_maps.cf
service postfix restart
Perform email sending test
echo "hello world" | mail -s test [email protected]
Enter the specified file to view
cd /home/vmail/
cat extmail.org/postmaster/Maildir/new/*localdomain
Email successfully received
Five, configure MRA service
Download dovecot and mysql combined use tool
yum install dovecot dovecot-mysql -y
Edit dovecot disk path related configuration
cd /etc/dovecot/conf.d/
vim 10-mail.conf
#修改24行
mail_location = maildir:/home/vmail/%d/%n/Maildir
#修改167行，指定运行用户uid
first_valid_uid = 600
Save and exit
Edit dovecot user authentication related configuration information
vim 10-auth.conf
Uncomment the 120 lines to make it authenticated by the database.
Save and exit, return to the upper-level directory, copy dovecot and MySQL combined configuration file to the current directory.
cp /usr/share/doc/dovecot-2.0.9/example-config/dovecot-sql.conf.ext .
Edit Dovecot and database connection related configuration
vim dovecot-sql.conf.ext：
#修改29行
driver = mysql
#修改63行
connect = host=localhost dbname=extmail user=extmail password=extmail
#取消73行注释
defaulf_pass_scheme = MD5
#修改102行
password_query = \
SELECT username, domain, password \
FROM mailbox WHERE username = '%u' AND domain = '%d'
#修改120行
user_query = SELECT maildir, 600 AS uid, 600 AS gid FROM mailbox WHERE username = '%u'
Save and exit, restart the service and start the test.
/etc/init.d/dovecot start
Download the test software and perform a connection test
yum -y install telnet
telnet localhost 110
user [email protected]
pass extmail
list
retr 1
Successfully connected.
Six, configure the wed interface
Edit the main Apache configuration file
vim /etc/httpd/conf/httpd.conf
Configure the virtual host, uncomment line 990 and add the following information at the end of the file.
<VirtualHost *:80>
ServerName mail.extmail.org
DocumentRoot /var/www/extsuite/extmail/html/
ScriptAlias /extmail/cgi /var/www/extsuite/extmail/cgi
Alias /extmail /var/www/extsuite/extmail/html
ScriptAlias /extman/cgi /var/www/extsuite/extman/cgi
Alias /extman /var/www/extsuite/extman/html
SuexecUserGroup vmail vmail
</VirtualHost>
Edit settings mail wed page file
cd /var/www/extsuite/extmail
chown vmail.vmail cgi/ -R
cp webmail.cf.default webmail.cf
Edit the main configuration file to complete the basic settings.
vim wedmail.cf
#修改127行：（当前邮件目录）
SYS_MAILDIR_BASE = /home/vmail
#修改136行：（当前数据库密码存储方式）
SYS_CRYPT_TYPE = plain
#修改139、140行：（数据库名与密码）
SYS_MYSQL_USER = extmail
SYS_MYSQL_PASS = extmail
Edit the configuration file of the administrator of the set mail wed page
cd /var/www/extsuite/extman
chown vmail.vmail cgi/ -R
cp webman.cf.default webman.cf
Edit the email wed page administrator configuration file to complete the basic settings.
vim webman.cf
#修改12行：（当前邮件目录）
SYS_MAILDIR_BASE = /home/vmail
#修改18行：（缓存目录）
SYS_SESS_DIR = /tmp/
#修改27行：（随机认证码长度）
SYS_CAPTCHA_LEN = 4
#修改124行：（当前数据库密码存储方式）
SYS_CRYPT_TYPE = plain
Seven, visit test.
1. Mail server settings
Install missing dependencies
cd
yum install *CGI perl-GD gcc* -y
yum -y install perl-GD-2.44-3.el6.x86_64.rpm
Installation log creation component
tar zxf Unix-Syslog-1.1.tar.gz
cd Unix-Syslog-1.1
perl Makefile.PL
make test
make install
Create storage directory
/var/www/extsuite/extman/daemon/cmdserver -d
Restart Apache service
service httpd restart
2. Client configuration
Configure DNS and restart the network card.
echo "DNS1=192.168.10.14" >> /etc/sysconfig/network-scripts/ifcfg-eth0
service network restart
Perform analytical testing
nslookup 192.168.10.14
Successfully analyze, open the graphical interface, and start to access the test.
init 5
3. Access test
Open the browser and enter the web address for ordinary users.
mail.extmail.org
Enter test account and default password
测试账户
postmaster
默认密码
extmail
Landed successfully
Test administrator login
mail.extmail.org/extman
Enter the set password
Carry out functional test and mass mailing test.
Log in to the test user to see if you have received it.
The group mail is successfully received, and the mail service is set up.
This article was reorganized by Vonmerlot on October 31, 2020.
Reprinting must indicate the source.