FQDN: hostname.dev.example.com

From: <root@dev.example.com>

main.cf:  #myhostname
          #mydomain
results:  From:<root@hostname.localdomain>


main.cf:  myhostname = hostname.dev.example.com
results:  From:<root@dev.example.com>


main.cf:  myhostname = hostname
          mydomain = dev.example.com
results:  From:<root@dev.example.com>


main.cf:  myhostname = hostname.dev
          mydomain = example.com
results:  From:<root@dev.example.com>


main.cf:  myhostname = hostname.dev.example.com
results:  Postfix error


main.cf:  myhostname = "hostname.dev.example.com"
results:  Postfix error


main.cf:  myhostname = hostname.dev.example
results:  From:<root@hostname.dev.example>


main.cf:  mydomain = dev.example.com
results:  From:<root@dev.example.com>


main.cf:  myhostname = hostname.dev
          myorigin = example.com
results:  From:<root@example.com>


main.cf:  myorigin = hostname.dev.example.com
results:  From:<root@dev.example.com>

From: <root@hostname.dev.example.com>

root@hostname.localdomain      root@hostname.dev.example.com