username@hp:~$ cat /etc/amavis/conf.d/05-node_id
use strict;

# $myhostname is used by amavisd-new for node identification, and it is
# important to get it right (e.g. for ESMTP EHLO, loop detection, and so on).

chomp($myhostname = `hostname --fqdn`);

# To manually set $myhostname, edit the following line with the correct Fully
# Qualified Domain Name (FQDN) and remove the # at the beginning of the line.
#
#$myhostname = "mail.example.com";

1;  # ensure a defined return
username@hp:~$