Postfix Configuration on Centos 5.x Rumi, December 5, 2011 Let's 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_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination' postconf -e 'inet_interfaces = all' postconf -e 'mynetworks = 127.0.0.0/8' We must edit /usr/lib/sasl2/smtpd.conf so that Postfix allows PLAIN and LOGIN logins. On a 64Bit Centos 5.0 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' After these configuration steps you should now have a /etc/postfix/main.cf that looks like this (I have removed all comments from it): cat /etc/postfix/main.cf queue_directory = /var/spool/postfix command_directory = /usr/sbin daemon_directory = /usr/libexec/postfix mail_owner = postfix inet_interfaces = all mydestination = $myhostname, localhost.$mydomain, localhost unknown_local_recipient_reject_code = 550 alias_maps = hash:/etc/aliases alias_database = hash:/etc/aliases debug_peer_level = 2 debugger_command = PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin xxgdb $daemon_directory/$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-2.3.3/samples readme_directory = /usr/share/doc/postfix-2.3.3/README_FILES smtpd_sasl_local_domain = smtpd_sasl_auth_enable = yes smtpd_sasl_security_options = noanonymous broken_sasl_auth_clients = yes smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination mynetworks = 127.0.0.0/8 smtpd_tls_auth_only = no smtp_use_tls = yes smtpd_use_tls = yes smtp_tls_note_starttls_offer = yes smtpd_tls_key_file = /etc/postfix/ssl/smtpd.key smtpd_tls_cert_file = /etc/postfix/ssl/smtpd.crt smtpd_tls_CAfile = /etc/postfix/ssl/cacert.pem smtpd_tls_loglevel = 1 smtpd_tls_received_header = yes smtpd_tls_session_cache_timeout = 3600s tls_random_source = dev:/dev/urandom 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 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 250-STARTTLS and 250-AUTH LOGIN PLAIN everything is fine. [root@server1 ssl]# telnet localhost 25 Trying 127.0.0.1… Connected to localhost.localdomain (127.0.0.1). Escape character is '^]'. 220 server1.example.com ESMTP Postfix ehlo localhost 250-server1.example.com 250-PIPELINING 250-SIZE 10240000 250-VRFY 250-ETRN 250-STARTTLS 250-AUTH LOGIN PLAIN 250-AUTH=LOGIN PLAIN 250-ENHANCEDSTATUSCODES 250-8BITMIME 250 DSN quit 221 2.0.0 Bye Connection closed by foreign host. Type quit to return to the system's shell. Configurations (Linux) CentOSPerfectPostfix