#!/usr/bin/perl

use strict;
use warnings;
use Mail::Sender;

my $file = '/path/to/file/with/html.sourcen';

open(my $fh,"<",$file) or die $!;
my $text = join('',<$fh>);
close $fh;

  my $sender = new Mail::Sender {
                smtp => 'smtp.isp.tld',
                from => 'test@your-domain.tld',
                auth => 'LOGIN',
                authid => 'username',
                authpwd => 'passwort',
                on_errors => undef,
        }  or die "Can't create the Mail::Sender object: $Mail::Sender::Error\n";

  $sender->OpenMultipart({to       => 'empfaenger@domain.tld',
                  subject  => "HTML test ", 
                  ctype    => "text/html; charset=iso-8859-1",
                  encoding => "quoted-printable"}) or die $Mail::Sender::Error,"\n";
  $sender->SendEnc($text);
  $sender->Close();