Hello, I want to share a documentation how to setup a mail server using CentOS 6.5 using Postfix as SMTP server and Dovecot as IMAP/POP3 server. Postfix is a well known Message Transfer Agent that mostly used today and Dovecot is also one of the widely used Mail User Agent.
In this documentation we use a CentOS 6.5 server and before we start, let's update the system.
A mail server needs to have a MX record in its DNS, so make sure we have that. It is also a good thing to set the PTR record pointing to our domain too.
# dig server.net -t ANY
;; ANSWER SECTION:
server.net. 86312 IN MX 10 mail.server.net.
server.net. 86306 IN A 192.168.45.32
server.net. 80528 IN NS ns2.server.net.
server.net. 80528 IN NS ns1.server.net.
Then install Postfix using yum if it's not already installed.
Edit Postfix configuration file main.cf,
# vi /etc/postfix/main.cf
This is a standard configuration,
queue_directory = /var/spool/postfix
command_directory = /usr/sbin
daemon_directory = /usr/libexec/postfix
data_directory = /var/lib/postfix
mail_owner = postfix
myhostname = mail.server.net
myorigin = $mydomain
inet_interfaces = all
inet_protocols = ipv4
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
unknown_local_recipient_reject_code = 550
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
home_mailbox = Maildir/
smtpd_banner = $myhostname ESMTP
debug_peer_level = 2
debugger_command =
PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin
ddd $daemon_directory/$process_name $process_id & sleep 5
sendmail_path = /usr/sbin/sendmail.postfix
newaliases_path = /usr/bin/newaliases.postfix
mailq_path = /usr/bin/mailq.postfix
setgid_group = postdrop
html_directory = no
manpage_directory = /usr/share/man
sample_directory = /usr/share/doc/postfix-2.6.6/samples
readme_directory = /usr/share/doc/postfix-2.6.6/README_FILES
# SASL configuration
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
smtpd_sasl_local_domain = $myhostname
smtpd_client_restrictions =
permit_mynetworks,
reject_unknown_client,
permit
smtpd_recipient_restrictions =
permit_mynetworks,
permit_auth_destination,
permit_sasl_authenticated,
reject
# TLS configuration
smtpd_use_tls = yes
smtpd_tls_key_file = /etc/pki/tls/private/ssl.key
smtpd_tls_cert_file = /etc/pki/tls/cert/ssl.crt
smtpd_tls_loglevel = 3
smtpd_tls_received_header = yes
smtpd_tls_session_cache_timeout = 3600s
tls_random_source = dev:/dev/urandom
Restart Postfix,
# service postfix restart
Install Dovecot using yum,
Edit Dovecot configuration file dovecot.conf,
# vi /etc/dovecot/dovecot.conf
protocols = imap pop3
listen = *
dict {
}
!include conf.d/*.conf
Edit 10-auth.conf,
# vi /etc/dovecot/conf.d/10-auth.conf
disable_plaintext_auth = no
auth_mechanisms = plain login
!include auth-system.conf.ext
Edit 10-mail.conf,
# vi /etc/dovecot/conf.d/10-mail.conf
mail_location = maildir:~/Maildir
mbox_write_locks = fcntl
Edit 10-master.conf,
# vi /etc/dovecot/conf.d/10-master.conf
service imap-login {
inet_listener imap {
}
inet_listener imaps {
}
}
service pop3-login {
inet_listener pop3 {
}
inet_listener pop3s {
}
}
service lmtp {
unix_listener lmtp {
}
}
service imap {
}
service pop3 {
}
service auth {
unix_listener auth-userdb {
}
unix_listener /var/spool/postfix/private/auth {
mode = 0666
user = postfix
group = postfix
}
}
service auth-worker {
}
service dict {
unix_listener dict {
}
}
Edit 10-ssl.conf,
# vi /etc/dovecot/conf.d/10-ssl.conf
ssl = yes
ssl_cert = </etc/pki/tls/cert/ssl.crt
ssl_key = </etc/pki/tls/private/ssl.key
Start Dovecot,
# service dovecot start
# chkconfig dovecot on
Test your Postfix installation by sending a message using our newly installed server. Use telnet on your mail server on port 25.
$ telnet mail.server.net 25
Trying 192.168.45.32...
Connected to mail.server.net.
Escape character is '^]'.
220 mail.server.net ESMTP
EHLO mail.server.net
250-mail.server.net
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
MAIL FROM: <admin@server.net>
250 2.1.0 Ok
RCPT TO: <user@gmail.com>
250 2.1.5 Ok
DATA
354 End data with <CR><LF>.<CR><LF>
From: Administrator <admin@server.net>
To: User <user@gmail.com>
Subject: Test Mail Server
Test Mail Server
.
250 2.0.0 Ok: queued as 54549110F
Check your Gmail inbox to see if the message sent successfully. Then check Dovecot using telnet on your mail server on port 143.
$ telnet mail.server.net 143
Trying 192.168.45.32...
Connected to mail.server.net.
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE STARTTLS AUTH=PLAIN AUTH=LOGIN] Dovecot ready.
aa login user password
aa OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE SORT SORT=DISPLAY THREAD=REFERENCES THREAD=REFS MULTIAPPEND UNSELECT CHILDREN NAMESPACE UIDPLUS LIST-EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH ESORT SEARCHRES WITHIN CONTEXT=SEARCH LIST-STATUS] Logged in
ab select INBOX
* FLAGS (\Answered \Flagged \Deleted \Seen \Draft $Forwarded)
* OK [PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft $Forwarded \*)] Flags permitted.
* 0 EXISTS
* 0 RECENT
* OK [UIDVALIDITY 1390092598] UIDs valid
* OK [UIDNEXT 7] Predicted next UID
* OK [HIGHESTMODSEQ 1] Highest
ab OK [READ-WRITE] Select completed.
ac logout
* BYE Logging out
ac OK Logout completed.
Connection closed by foreign host.
Congratulation! Now you have a working SMTP and IMAP/POP3 server! :D
in CentOS 6.5
