Postfix

Aliases

The aliases are grouped in /etc/aliases

# See man 5 aliases for format
postmaster:    root
root:		me@mydomain.org
leopardb:	me@mydomain.org

After modifying, do not forget to run newaliases

Test email one liner

Using sendmail, root email address in /etc/aliases

echo -e "Subject:Test - delete me\n\nPing\n" | sendmail root
echo -e "To:leo@domain.com\nSubject:Test - delete me\n\nPing\n" | sendmail root
echo -e "From:authorized@domain.com\nTo:leo@domain.com\nSubject:Test - delete me\n\nPing\n" | sendmail root
(echo -e "Subject:Test - delete me\n\nPing\n"; dmidecode ) | sendmail root

Omitting the To: will make the email appear as sent to “undisclosed recipients”.

Authentication

You must have installed the required SASL libraries:

apt install libsasl2-modules

Create a password file sasl_passwd looking like this:

external.smtpserver.com:25 login:password

the server part has to be written exactly as it appears in main.cf

Protect it:

chown root:root sasl_passwd
chmod 600 sasl_passwd

Create the hash:

postmap sasl_passwd

Mail queue

List emails in the queue

sendmail -bp

Remove emails in queue (postsuper – Postfix superintendent):

postsuper -d mail_id
postsuper -d ALL

Relay

To relay mail for other clients from the network 192.168.0.0/24

mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 192.168.0.0/24

inet_interfaces = all
inet_protocols = ipv4