#!/usr/bin/perl -w
use strict;
use Net::SMTP;
use IO::Scalar;
my $smtp;
my $debug = '';
tie *STDERR, 'IO::Scalar', \$debug;

$smtp = Net::SMTP->new('your.smtp.server',
                           Hello => 'a.domain.it.accepts',
                           Timeout => 30,
                           Debug   => 1,
                          );
$smtp->quit();
untie *STDERR;
print grep {/SIZE/} (split(/\n/,$debug));