See also SSMTP

http://www.mechanicalfish.net/classic-blog/posts/92-configuring-postfix-relay-mail-secure-host/

http://www.stefanolocati.it/blog/?p=737

Gmail: http://www.stevemccann.net/2012/12/changing-freepbx-smtp-server-to-gmail.html

From Address: http://www.cyberciti.biz/tips/howto-postfix-masquerade-change-email-mail-address.html

There are various reasons that you may want to configure Postfix to relay all mail to a 'smarthost'.

• Spam filtering
• Port blocking by your ISP
• SPF DNS record doesn't permit your IP to send mail
• Blacklisted IP address
• Etc.

You can copy and paste the following into an editor, then adjust the $SMTPHOST and $USERPASS variables for your needs. Then, as root, paste it to the command line:

FILE=/etc/postfix/password
SMTPHOST=your.mailserver.domain
#SMTPHOST=your.mailserver.domain:587
#SMTPHOST=[123.123.123.123]:587
USERPASS=user:pass

# This will overwrite any existing contents
cat << EOF > $FILE
#smtp.isp.com       username:password
$SMTPHOST  $USERPASS
EOF

chown root:root $FILE
chmod 0600 $FILE
postmap hash:$FILE

postconf -e "relayhost = $SMTPHOST"
postconf -e 'smtp_sasl_auth_enable = yes'
postconf -e 'smtp_sasl_password_maps = hash:/etc/postfix/password'
postconf -e 'smtp_sasl_security_options ='

/etc/init.d/postfix reload

Additionally, you may be forced to use TLS which may authenticate differently. Here are some additional steps to implement TLS.

Debian/Ubuntu:

apt-get install libsasl2-modules

Redhat/CentOS:

yum install cyrus-sasl-plain

First we configure the authentication credentials for Postfix.

Newer FreePBX machines create and maintain /etc/postfix/sasl_passwd for you.

Edit /etc/postfix/password to point to a TLS capable host:port:

SMTPHOST=your.mailserver.domain:587

postmap hash:/etc/postfix/password

Here we enable TLS in Postfix:

postconf -e 'smtp_use_tls=yes'
/etc/init.d/postfix reload

Envelope-From: http://serverfault.com/questions/533912/how-do-i-change-the-envelope-from-in-postfix

Some servers require the envelope-from header to be a valid user in order to accept mail via authenticated SMTP.

vim /etc/postfix/canonical

This is not a best practice…it's something you might use on a PBX just to get it to send mail.

Append something like this to force all mail to have the specified envelope-from.

# Use the empty regexp to map *any* address to the desired envelope sender.
// pbx@yourdomain.tld

postmap /etc/postfix/canonical
postconf -e "canonical_classes = envelope_sender"
postconf -e "canonical_maps = regexp:/etc/postfix/canonical"
postfix reload