Tuesday, February 9, 2010

Installing Postfix/Dovecot with SMTP-AUTH and TLS on CentOS x64

SkyHi @ Tuesday, February 09, 2010

Postfix is a free open source mail transfer agent (MTA), a computer program for the routing and delivery of email. It is intended as a fast, easy-to-administer, and secure alternative to the widely-used Sendmail MTA. Formerly known as VMailer and IBM Secure Mailer, it was originally written by Wietse Venema during a stay at the IBM Thomas J. Watson Research Center, and continues to be actively developed today. Postfix was first released in mid-1999.

Dovecot is an open source IMAP and POP3 server for Linux/UNIX-like systems, written primarily with security in mind. Developed by Timo Sirainen, Dovecot was first released in July 2002. Dovecot primarily aims to be a lightweight, fast and easy to set up open source mailserver.

Dovecot can work with standard mbox, Maildir, and its own experimental native high-performance dbox formats. [1] It is fully compatible with UW IMAP and Courier IMAP servers' implementation of them, as well as mail clients accessing the mailboxes directly.

Notes: If you are on Windows OS, you should download putty http://www.chiark.greenend.org.uk/~sgtatham/putty/ to SSH.

Now we install Postfix and Dovecot (Dovecot will be our POP3/IMAP server):

yum install cyrus-sasl cyrus-sasl-devel cyrus-sasl-gssapi cyrus-sasl-md5 cyrus-sasl-plain postfix dovecot

Next we configure SMTP-AUTH and TLS:

postconf -e 'smtpd_sasl_local_domain ='
postconf -e 'smtpd_sasl_auth_enable = yes'
postconf -e 'smtpd_sasl_security_options = noanonymous'
postconf -e 'broken_sasl_auth_clients = yes'
postconf -e 'smtpd_sasl_authenticated_header = yes'
postconf -e 'smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination'
postconf -e 'inet_interfaces = all'
postconf -e 'mynetworks ='

We must edit /usr/lib/sasl2/smtpd.conf so that Postfix allows PLAIN and LOGIN logins. On a 64Bit Centos 5.2 you must edit the file /usr/lib64/sasl2/smtpd.conf instead. It should look like this:

vi /usr/lib/sasl2/smtpd.conf

pwcheck_method: saslauthd
mech_list: plain login

Afterwards we create the certificates for TLS:

mkdir /etc/postfix/ssl
cd /etc/postfix/ssl/
openssl genrsa -des3 -rand /etc/hosts -out smtpd.key 1024

chmod 600 smtpd.key
openssl req -new -key smtpd.key -out smtpd.csr

openssl x509 -req -days 3650 -in smtpd.csr -signkey smtpd.key -out smtpd.crt

openssl rsa -in smtpd.key -out smtpd.key.unencrypted

mv -f smtpd.key.unencrypted smtpd.key
openssl req -new -x509 -extensions v3_ca -keyout cakey.pem -out cacert.pem -days 3650

Next we configure Postfix for TLS:

postconf -e 'smtpd_tls_auth_only = no'
postconf -e 'smtp_use_tls = yes'
postconf -e 'smtpd_use_tls = yes'
postconf -e 'smtp_tls_note_starttls_offer = yes'
postconf -e 'smtpd_tls_key_file = /etc/postfix/ssl/smtpd.key'
postconf -e 'smtpd_tls_cert_file = /etc/postfix/ssl/smtpd.crt'
postconf -e 'smtpd_tls_CAfile = /etc/postfix/ssl/cacert.pem'
postconf -e 'smtpd_tls_loglevel = 1'
postconf -e 'smtpd_tls_received_header = yes'
postconf -e 'smtpd_tls_session_cache_timeout = 3600s'
postconf -e 'tls_random_source = dev:/dev/urandom'

Then we set the hostname in our Postfix installation (make sure you replace server1.example.com with your own hostname):

postconf -e 'myhostname = drupalab.com'

By default, CentOS' Dovecot daemon provides only IMAP and IMAPs services. Because we also want POP3 and POP3s we must configure Dovecot to do so. We edit /etc/dovecot.conf and enable the line protocols = imap imaps pop3 pop3s:

vi /etc/dovecot.conf

# Base directory where to store runtime data.
#base_dir = /var/run/dovecot/

# Protocols we want to be serving: imap imaps pop3 pop3s
# If you only want to use dovecot-auth, you can set this to "none".
protocols = imap imaps pop3 pop3s

# IP or host address where to listen in for connections. It's not currently
# possible to specify multiple addresses. "*" listens in all IPv4 interfaces.
# "[::]" listens in all IPv6 interfaces, but may also listen in all IPv4
# interfaces depending on the operating system.

Now start Postfix, saslauthd, and Dovecot:

chkconfig --levels 235 sendmail off
chkconfig --levels 235 postfix on
chkconfig --levels 235 saslauthd on
chkconfig --levels 235 dovecot on
/etc/init.d/sendmail stop
/etc/init.d/postfix start
/etc/init.d/saslauthd start
/etc/init.d/dovecot start

To see if SMTP-AUTH and TLS work properly now run the following command:

telnet localhost 25

After you have established the connection to your Postfix mail server type

ehlo localhost

If you see the lines




everything is fine.

- bash## telnet localhost 25
Connected to localhost.localdomain (
Escape character is '^]'.
220 server1.example.com ESMTP Postfix
ehlo localhost
250-SIZE 10240000
250 DSN
221 2.0.0 Bye
Connection closed by foreign host.
- bash#



to return to the system's shell.


Dovecot uses Maildir format (not mbox), so if you install ISPConfig on the server, please make sure you enable Maildir under Management -> Server -> Settings -> Email. ISPConfig will then do the necessary configuration.

If you do not want to install ISPConfig, then you must configure Postfix to deliver emails to a user's Maildir (you can also do this if you use ISPConfig - it doesn't hurt ;-)):

postconf -e 'home_mailbox = Maildir/'
postconf -e 'mailbox_command ='
/etc/init.d/postfix restart

To email from Drupal, you have to install "SMTP Authentication Support" module to send email thru SMTP Server.