Install and Configure Postfix to send mail using Gmail




1. Install postfix and other requiired packages

yum install postfix mailx cyrus-sasl-plain m4

2. Create a file named client-info in /etc/mail/auth/

nano /etc/mail/auth/client-info “U:root” “I:username” “P:password” M:”PLAIN” “U:root” “I:username” “password” M:”PLAIN”
AuthInfo:”″ U:”root” I:”username” P:”password” M:”PLAIN”

3. Create the db of client-info file

makemap hash client-info < client-info

chmod 600 /etc/mail/auth/*

4. create the certificate

cd /etc/mail/certs/

make sendmail.pem

5. Change /etc/mail/ like below

dnl #
dnl # This is the sendmail macro config file for m4. If you make changes to
dnl # /etc/mail/, you will need to regenerate the
dnl # /etc/mail/ file by confirming that the sendmail-cf package is
dnl # installed and then performing a
dnl #
dnl # /etc/mail/make
dnl #
VERSIONID(`setup for linux’)dnl
dnl #
dnl # Do not advertize sendmail version.
dnl #
dnl define(`confSMTP_LOGIN_MSG’, `$j Sendmail; $b’)dnl
dnl #
dnl # default logging level is 9, you might want to set it higher to
dnl # debug the configuration
dnl #
dnl define(`confLOG_LEVEL’, `9′)dnl
dnl #
dnl # Uncomment and edit the following line if your outgoing mail needs to
dnl # be sent out through an external mail server:
dnl #
define(`SMART_HOST’, `’)dnl
define(`RELAY_MAILER_ARGS’, `TCP $h 587′)dnl
define(`ESMTP_MAILER_ARGS’, `TCP $h 587′)dnl

dnl #
define(`confDEF_USER_ID’, “8:12”)dnl
dnl define(`confAUTO_REBUILD’)dnl
define(`confTO_CONNECT’, `1m’)dnl
define(`confTRY_NULL_MX_LIST’, `True’)dnl
define(`confDONT_PROBE_INTERFACES’, `True’)dnl
define(`PROCMAIL_MAILER_PATH’, `/usr/bin/procmail’)dnl
define(`ALIAS_FILE’, `/etc/aliases’)dnl
define(`STATUS_FILE’, `/var/log/mail/statistics’)dnl
define(`UUCP_MAILER_MAX’, `2000000′)dnl
define(`confUSERDB_SPEC’, `/etc/mail/userdb.db’)dnl
define(`confPRIVACY_FLAGS’, `authwarnings,novrfy,noexpn,restrictqrun’)dnl
define(`confAUTH_OPTIONS’, `A’)dnl
dnl #
dnl # The following allows relaying if the user authenticates, and disallows
dnl # plaintext authentication (PLAIN/LOGIN) on non-TLS links
dnl #
define(`confAUTH_OPTIONS’, `A p’)dnl
dnl #
dnl # PLAIN is the preferred plaintext authentication method and used by
dnl # Mozilla Mail and Evolution, though Outlook Express and other MUAs do
dnl # use LOGIN. Other mechanisms should be used if the connection is not
dnl # guaranteed secure.
dnl # Please remember that saslauthd needs to be running for AUTH.
dnl #
FEATURE(`authinfo’,`hash /etc/mail/auth/client-info.db’)dnl
FEATURE(`access_db’, `hash -T -o /etc/mail/access.db’)dnl
dnl #
dnl # Rudimentary information on creating certificates for sendmail TLS:
dnl # cd /etc/pki/tls/certs; make sendmail.pem
dnl # Complete usage:
dnl # make -C /etc/pki/tls/certs usage
dnl #
define(`confCACERT_PATH’, `/etc/pki/tls/certs’)dnl
define(`confCACERT’, `/etc/pki/tls/certs/ca-bundle.crt’)dnl
define(`confSERVER_CERT’, `/etc/pki/tls/certs/sendmail.pem’)dnl
define(`confSERVER_KEY’, `/etc/pki/tls/certs/sendmail.pem’)dnl
define(`confCLIENT_CERT’, `/etc/pki/tls/certs/sendmail.pem’)dnl
define(`confCLIENT_KEY’, `/etc/pki/tls/certs/sendmail.pem’)dnl
dnl #
dnl # This allows sendmail to use a keyfile that is shared with OpenLDAP’s
dnl # slapd, which requires the file to be readble by group ldap
dnl #
dnl define(`confDONT_BLAME_SENDMAIL’, `groupreadablekeyfile’)dnl
dnl #
dnl define(`confTO_QUEUEWARN’, `4h’)dnl
dnl define(`confTO_QUEUERETURN’, `5d’)dnl
dnl define(`confQUEUE_LA’, `12′)dnl
dnl define(`confREFUSE_LA’, `18′)dnl
define(`confTO_IDENT’, `0′)dnl
dnl FEATURE(delay_checks)dnl
FEATURE(`no_default_msa’, `dnl’)dnl
FEATURE(`smrsh’, `/usr/sbin/smrsh’)dnl
FEATURE(`mailertable’, `hash -o /etc/mail/mailertable.db’)dnl
FEATURE(`virtusertable’, `hash -o /etc/mail/virtusertable.db’)dnl
dnl #
dnl # The following limits the number of processes sendmail can fork to accept
dnl # incoming messages or process its message queues to 20.) sendmail refuses
dnl # to accept connections once it has reached its quota of child processes.
dnl #
dnl define(`confMAX_DAEMON_CHILDREN’, `20′)dnl
dnl #
dnl # Limits the number of new connections per second. This caps the overhead
dnl # incurred due to forking new sendmail processes. May be useful against
dnl # DoS attacks or barrages of spam. (As mentioned below, a per-IP address
dnl # limit would be useful but is not available as an option at this writing.)
dnl #
dnl define(`confCONNECTION_RATE_THROTTLE’, `3′)dnl
dnl #
dnl # The -t option will retry delivery if e.g. the user runs over his quota.
dnl #
FEATURE(local_procmail, `’, `procmail -t -Y -a $h -d $u’)dnl
FEATURE(`access_db’, `hash -T -o /etc/mail/access.db’)dnl
dnl #
dnl # For using Cyrus-IMAPd as POP3/IMAP server through LMTP delivery uncomment
dnl # the following 2 definitions and activate below in the MAILER section the
dnl # cyrusv2 mailer.
dnl #
dnl define(`confLOCAL_MAILER’, `cyrusv2′)dnl
dnl define(`CYRUSV2_MAILER_ARGS’, `FILE /var/lib/imap/socket/lmtp’)dnl
dnl #
dnl # The following causes sendmail to only listen on the IPv4 loopback address
dnl # and not on any other network devices. Remove the loopback
dnl # address restriction to accept email from the internet or intranet.
dnl #
DAEMON_OPTIONS(`Port=smtp,Addr=, Name=MTA’)dnl
dnl #
dnl # The following causes sendmail to additionally listen to port 587 for
dnl # mail from MUAs that authenticate. Roaming users who can’t reach their
dnl # preferred sendmail daemon due to port 25 being blocked or redirected find
dnl # this useful.
dnl #
DAEMON_OPTIONS(`Port=submission, Name=MSA, M=Ea’)dnl
dnl #
dnl # The following causes sendmail to additionally listen to port 465, but
dnl # starting immediately in TLS mode upon connecting. Port 25 or 587 followed
dnl # by STARTTLS is preferred, but roaming clients using Outlook Express can’t
dnl # do STARTTLS on ports other than 25. Mozilla Mail can ONLY use STARTTLS
dnl # and doesn’t support the deprecated smtps; Evolution /etc/mail/

6. Compile Sendmail Configurations

m4 /etc/mail/ > /etc/mail/

7. Restart Sendmail Service

service sendmail restart