postfix basic essentials

check postfix supported lookup table types: "sudo postconf -m"

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regexp
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sudo nano /etc/postfix/header_checks

/^Received:/ IGNORE
/^Reply-To:/ IGNORE
/^X-/ IGNORE

sudo nano /etc/postfix/main.cf

# header checks lookup

header_checks = regexp:/etc/postfix/header_checks

# lookup tables

virtual_alias_maps = hash:/etc/postfix/virtual
smtp_generic_maps = hash:/etc/postfix/generic

# relay to external sender

smtp_sasl_auth_enable = yes
smtp_sasl_security_options = noanonymous
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
relayhost = [domain.com]:587

# generic - virtual - sasl_passwd

generic: www-data user@domain.com
virtual: @domain.com user@domain.net
sasl_passwd: domain.com user@domain.com:pass

# same goes to other hash tables
sudo postmap /etc/postfix/generic