#!/usr/bin/perl -w

use Socket;
die "No host name given" if not defined $ARGV[0];
if (socket(SOCK, PF_INET, SOCK_STREAM, getprotobyname('tcp')) and
    connect(SOCK, sockaddr_in(25, inet_aton($ARGV[0])))) {
    my $line = <SOCK>;
    exit 0 if defined $line and $line =~ /^2/;
}
# Error:
print "smtp on $ARGV[0]\n";
exit 1;