Postfix

cat /etc/postfix/vi main.cf.new

myhostname = tango.info
mydestination = localhost, $myhostname
myorigin = /etc/mailname

cat /etc/postfix/main.cf
myorigin = /etc/mailname
mydomain = tango.info
myhostname = tango.info

/etc/mailname

cat /etc/mailname
tango.info (CHANGE to anna.info - some email will now have 
 smtp.mailfrom=xxx@anna.info
 Return-Path: <xxx@anna.info>
 From: xxx <xxx@anna.info>
 but message ID still 1234567890@tango.info
 )

mydomain

cat /etc/postfix/main.cf
myorigin = /etc/mailname
mydomain = tango.info
myhostname = tango.info

CHANGE to anna.info - no influence?

myhostname

CHANGE to anna.info - messag-ID now 12345789@anna.info