smtp-cli

#!/usr/bin/perl

# 
# Command line SMTP client with STARTTLS, SMTP-AUTH and IPv6 support.
# Michal Ludvig <michal@logix.cz>, 2003-2009
# See http://www.logix.cz/michal/devel/smtp-cli for details.
# Thanks to all contributors for ideas and fixes!
#

my $version = "2.6";

# 
# ChangeLog:
# * Version 2.6    (2009-08-05)
#   - Message building fixed for plaintext+attachment case.
#   - Auto-enable AUTH as soon as --user parameter is used.
#     (previously --enable-auth or --auth-plain had to be used
#      together with --user, that was confusing).
#   - New --print-only parameter for displaying the composed
#     MIME message without sending.
#   - All(?) non-standard modules are now optional.
#   - Displays local and remote address on successfull connect.
#
# * Version 2.5    (2009-07-21)
#   - IPv6 support provided the required modules are 
#     available.
#
# * Version 2.1    (2008-12-08)
#   - Make the MIME modules optional. Simply disable
#     the required functionality if they're not available.
#
# * Version 2.0    (2008-11-18)
#   - Support for message building through MIME::Lite, 
#     including attachments, multipart, etc.
#
# * Version 1.1    (2006-08-26)
#   - STARTTLS and AUTH support
#
# * Version 1.0
#   - First public version
# 
# This program is licensed under GNU Public License v3 (GPLv3)
# 

## Require Perl 5.8 or higher -> we need open(.., .., \$variable) construct
require 5.008;

use strict;
use IO::Socket::INET;
use MIME::Base64 qw(encode_base64 decode_base64);
use Getopt::Long;
use Socket qw(:DEFAULT :crlf);

my ($user, $pass, $host, $port, $addr_family,
    $use_login, $use_plain, $use_cram_md5,
    $ehlo_ok, $auth_ok, $starttls_ok, $verbose, 
    $hello_host, $from, @to, $datasrc,
    $missing_modules_ok, $missing_modules_count,
    $subject, $body_plain, $body_html, $print_only,
	@attachments, @attachments_inline,
    $sock, $built_message);

$host = 'localhost';
$port = 'smtp(25)';
$addr_family = AF_UNSPEC;
$hello_host = 'localhost';
$verbose = 0;
$use_login = 0;
$use_plain = 0;
$use_cram_md5 = 0;
$starttls_ok = 1;
$auth_ok = 0;
$ehlo_ok = 1;
$missing_modules_ok = 0;
$missing_modules_count = 0;
$print_only = 0;

# Get command line options.
GetOptions (
	'host|server=s' => \$host,
	'port=i' => \$port, 
	'4|ipv4' => sub { $addr_family = AF_INET; },
	'6|ipv6' => sub { $addr_family = AF_INET6; },
	'user=s' => \$user, 'password=s' => \$pass,
	'auth-login' => \$use_login, 
	'auth-plain' => \$use_plain,
	'auth-cram-md5' => \$use_cram_md5, 
	'disable-ehlo' => sub { $ehlo_ok = 0; },
	'force-ehlo' => sub { $ehlo_ok = 2; },
	'hello-host|ehlo-host|helo-host=s' => \$hello_host,
	'auth|enable-auth' => \$auth_ok,
	'disable-starttls|disable-tls|disable-ssl' => 
		sub { $starttls_ok = 0; },
	'from|mail-from=s' => \$from,
	'to|rcpt-to=s' => \@to,
	'data=s' => \$datasrc,
	'subject=s' => \$subject,
	'body|body-plain=s' => \$body_plain,
	'body-html=s' => \$body_html,
	'attachment|attach=s' => \@attachments,
	'attachment-inline|attach-inline=s' => \@attachments_inline,
	'print-only' => \$print_only,
	'missing-modules-ok' => \$missing_modules_ok,
	'v|verbose+' => \$verbose,
	'version' => sub { &version() },
	'help' => sub { &usage() } );

#### Try to load optional modules

## IO::Socket::SSL and Net::SSLeay are optional
my $have_ssl = eval { require IO::Socket::SSL; require Net::SSLeay; 1; };
if (not $have_ssl and not $missing_modules_ok) {
	warn("!!! IO::Socket::SSL and/or Net::SSLeay modules are not found\n");
	warn("!!! These modules are required for STARTTLS support\n");
	$missing_modules_count += 2;
}

## IO::Socket::INET6 and Socket6 are optional
my $socket6 = eval { require IO::Socket::INET6; require Socket6; 1; };
if (not $socket6) {
	if ($addr_family == AF_INET6) {
		die("!!! IO::Socket::INET6 and Socket6 modules are not found\nIPv6 support is not available\n");
	}
	if (not $missing_modules_ok) {
		warn("!!! IO::Socket::INET6 -- optional module not found\n");
		warn("!!! Socket6 -- optional module not found\n");
		warn("!!! These modules are required for IPv6 support\n\n");
		$missing_modules_count += 2;
	}
}

## MIME::Lite dependency is optional
my $mime_lite = eval { require MIME::Lite; 1; };
if (not $mime_lite and not $missing_modules_ok) {
	warn("!!! MIME::Lite -- optional module not found\n");
	warn("!!! Used for composing messages from --subject, --body, --attachment, etc.\n\n");
	$missing_modules_count++;
}

## File::Type dependency is optional
my $file_type = eval { require File::Type; File::Type->new(); };
if (not $file_type and not $missing_modules_ok) {
	warn("!!! File::Type -- optional module not found\n");
	warn("!!! Used for guessing MIME types of attachments\n\n");
	$missing_modules_count++;
}

## Term::ReadKey dependency is optional
my $have_term_readkey = eval { require Term::ReadKey; 1; };
if (not $have_term_readkey and not $missing_modules_ok) {
	warn("!!! Term::ReadKey -- optional module not found\n");
	warn("!!! Used for hidden reading SMTP password from the terminal\n\n");
	$missing_modules_count++;
}

my $have_hmac_md5 = eval { require Digest::HMAC_MD5; 1; };
if (not $have_hmac_md5 and not $missing_modules_ok) {
	if ($use_cram_md5) {
		die("!!! CRAM-MD5 authentication is not available because Digest::HMAC_MD5 module is missing\n");
	}
	warn("!!! Digest::HMAC_MD5 -- optional module missing\n");
	warn("!!! Used for CRAM-MD5 authentication method\n");
	$missing_modules_count++;
}

## Advise about --missing-modules-ok parameter
if ($missing_modules_count) {
	warn("!!! Use --missing-modules-ok if you don't need the above listed modules\n");
	warn("!!! and don't want to see this message again.\n\n");
}

## Accept hostname with port number as host:port
if ($host =~ /^(.*):(.*)$/)
{
	$host = $1;
	$port = $2;
}

# Build the MIME message if required
if (defined($subject) or defined($body_plain) or defined($body_html) or
    	@attachments or @attachments_inline) {
	if (not $mime_lite) {
		die("Module MIME::Lite is not available. Unable to build the message, sorry.\n".
		    "Use --data and provide a complete email payload including headers instead.\n");
	}
	if (defined($datasrc)) {
		die("Requested building a message and at the same time used --data parameter.\n".
		    "That's not possible, sorry.\n");
	}
	if (defined($body_plain) and -f $body_plain) {
		local $/=undef;
		open(FILE, $body_plain);
		$body_plain = <FILE>;
		close(FILE);
	}
	if (defined($body_html) and -f $body_html) {
		local $/=undef;
		open(FILE, $body_html);
		$body_html = <FILE>;
		close(FILE);
	}
	my $message = &build_message();

	open(BUILT_MESSAGE, "+>", \$built_message);
	$datasrc = "///built_message";
	if ($print_only) {
		$message->print();
		exit(0);
	} else {
		$message->print(\*BUILT_MESSAGE);
	}
	seek(BUILT_MESSAGE, 0, 0);
}

# Username was given -> enable AUTH
if ($user)
	{ $auth_ok = 1; }

# If at least one --auth-* option was given, enable AUTH.
if ($use_login + $use_plain + $use_cram_md5 > 0)
	{ $auth_ok = 1; }

# If --enable-auth was given, enable all AUTH methods.
elsif ($auth_ok && ($use_login + $use_plain + $use_cram_md5 == 0))
{
	$use_login = 1;
	$use_plain = 1;
	$use_cram_md5 = 1 if ($have_hmac_md5);
}

# Exit if user haven't specified username for AUTH.
if ($auth_ok && !defined ($user))
	{ die ("SMTP AUTH support requested without --user\n"); }

# Ask for password if it wasn't supplied on the command line.
if ($auth_ok && defined ($user) && !defined ($pass))
{
	if ($have_term_readkey) {
		# Set echo off.
		Term::ReadKey::ReadMode (2);
	} else {
		warn ("Module Term::ReadKey not available - password WILL NOT be hidden!!!\n");
	}
	printf ("Enter password for %s@%s : ", $user, $host);
	$pass = <>;
	if ($have_term_readkey) {
		# Restore echo.
		Term::ReadKey::ReadMode (0);
		printf ("\n");
	}
	exit if (! defined ($pass));
	chop ($pass);
}

# Connect to the SMTP server.
my %connect_args = (
	PeerAddr => $host,
	PeerPort => $port,
	Proto => 'tcp',
	Timeout => 5);
if ($socket6) {
	$connect_args{'Domain'} = $addr_family;
	$sock = IO::Socket::INET6->new(%connect_args) or die ("Connect failed: $@\n");
} else {
	$sock = IO::Socket::INET->new(%connect_args) or die ("Connect failed: $@\n");
}

if ($verbose >= 1) {
	my $addr_fmt = "%s";
	$addr_fmt = "[%s]" if ($sock->sockhost() =~ /:/); ## IPv6 connection

	printf ("Connection from $addr_fmt:%s to $addr_fmt:%s\n",
		$sock->sockhost(), $sock->sockport(),
		$sock->peerhost(), $sock->peerport());
}

my ($code, $text);
my (%features);

# Wait for the welcome message of the server.
($code, $text) = &get_line ($sock);
die ("Unknown welcome string: '$code $text'\n") if ($code != 220);
$ehlo_ok-- if ($text !~ /ESMTP/);

# Send EHLO
&say_hello ($sock, $ehlo_ok, $hello_host, \%features) or exit (1);

# Run the SMTP session
&run_smtp ();

# Good bye...
&send_line ($sock, "QUIT\n");
($code, $text) = &get_line ($sock);
die ("Unknown QUIT response '$code'.\n") if ($code != 221);

exit 0;

# This is the main SMTP "engine".
sub run_smtp
{
	# See if we could start encryption
	if ((defined ($features{'STARTTLS'}) || defined ($features{'TLS'})) && $starttls_ok && !$have_ssl)
	{
		warn ("Module IO::Socket::SSL is missing - STARTTLS support disabled.\n");
		warn ("Use --disable-starttls or install the modules to avoid this warning.\n");
		undef ($features{'STARTTLS'});
		undef ($features{'TLS'});
	}

	if ((defined ($features{'STARTTLS'}) || defined ($features{'TLS'})) && $starttls_ok)
	{
		printf ("Starting TLS...\n") if ($verbose >= 1);

		# Do Net::SSLeay initialization
		Net::SSLeay::load_error_strings();
		Net::SSLeay::SSLeay_add_ssl_algorithms();
		Net::SSLeay::randomize();
	
		&send_line ($sock, "STARTTLS\n");
		($code, $text) = &get_line ($sock);
		die ("Unknown STARTTLS response '$code'.\n") if ($code != 220);
		
		if (! IO::Socket::SSL::socket_to_SSL($sock, 
			SSL_version => 'SSLv3 TLSv1'))
		{
			die ("STARTTLS: ".IO::Socket::SSL::errstr()."\n"); 
		}
		
		if ($verbose >= 1)
		{
			printf ("Using cipher: %s\n", $sock->get_cipher ());
			printf ("%s", $sock->dump_peer_certificate());
		}

		# Send EHLO again (required by the SMTP standard).
		&say_hello ($sock, $ehlo_ok, $hello_host, \%features) or return 0;
	}
	
	# See if we should authenticate ourself
	if (defined ($features{'AUTH'}) && $auth_ok)
	{
		printf ("AUTH method (%s): ", $features{'AUTH'}) if ($verbose >= 1);

		## Try DIGEST-MD5 first
		# Actually we won't. It never worked reliably here.
		# After all DIGEST-MD5 is on a way to deprecation
		# see this thread: http://www.imc.org/ietf-sasl/mail-archive/msg02996.html

		# Instead use CRAM-MD5 if supported by the server
		if ($features{'AUTH'} =~ /CRAM-MD5/i && $use_cram_md5)
		{
			printf ("using CRAM-MD5\n") if ($verbose >= 1);
			&send_line ($sock, "AUTH CRAM-MD5\n");
			($code, $text) = &get_line ($sock);
			if ($code != 334)
				{ die ("AUTH CRAM-MD5 failed: $code $text\n"); }
	
			my $response = &encode_cram_md5 ($text, $user, $pass);
			&send_line ($sock, "%s\n", $response);
			($code, $text) = &get_line ($sock);
			if ($code != 235)
				{ die ("AUTH CRAM-MD5 failed: $code $text\n"); }
		}
		# Eventually try LOGIN method
		elsif ($features{'AUTH'} =~ /LOGIN/i && $use_login)
		{
			printf ("using LOGIN\n") if ($verbose >= 1);
			&send_line ($sock, "AUTH LOGIN\n");
			($code, $text) = &get_line ($sock);
			if ($code != 334)
				{ die ("AUTH LOGIN failed: $code $text\n"); }
			
			&send_line ($sock, "%s\n", encode_base64 ($user, ""));

			($code, $text) = &get_line ($sock);
			if ($code != 334)
				{ die ("AUTH LOGIN failed: $code $text\n"); }
			
			&send_line ($sock, "%s\n", encode_base64 ($pass, ""));

			($code, $text) = &get_line ($sock);
			if ($code != 235)
				{ die ("AUTH LOGIN failed: $code $text\n"); }
		}
		# Or finally PLAIN if nothing else was supported.
		elsif ($features{'AUTH'} =~ /PLAIN/i && $use_plain)
		{
			printf ("using PLAIN\n") if ($verbose >= 1);
			&send_line ($sock, "AUTH PLAIN %s\n", 
				encode_base64 ("$user\0$user\0$pass", ""));
			($code, $text) = &get_line ($sock);
			if ($code != 235)
				{ die ("AUTH PLAIN failed: $code $text\n"); }
		}
		# Complain otherwise.
		else
		{
			warn ("No supported authentication method\n".
			      "advertised by the server.\n");
			return 0;
		}
		
		printf ("Authentication of $user\@$host succeeded\n") if ($verbose >= 1);
	}
	
	# We can do a relay-test now if a recipient was set.
	if ($#to >= 0)
	{
		if (!defined ($from))
		{
			warn ("From: address not set. Using empty one.\n");
			$from = "";
		}
		&send_line ($sock, "MAIL FROM: <%s>\n", $from);
		($code, $text) = &get_line ($sock);
		if ($code != 250)
		{
			warn ("MAIL FROM failed: '$code $text'\n");
			return 0;
		}

		my $i;
		for ($i=0; $i <= $#to; $i++)
		{
			&send_line ($sock, "RCPT TO: <%s>\n", $to[$i]);
			($code, $text) = &get_line ($sock);
			if ($code != 250)
			{
				warn ("RCPT TO <".$to[$i]."> ".
				      "failed: '$code $text'\n");
				return 0;
			}
		}
	}

	# Wow, we should even send something!
	if (defined ($datasrc))
	{
		if ($datasrc eq "///built_message")
		{
			*MAIL = *BUILT_MESSAGE;
		}
		elsif ($datasrc eq "-")
		{
			*MAIL = *STDIN;
		}
		elsif (!open (MAIL, $datasrc))
		{
			warn ("Can't open file '$datasrc'\n");
			return 0;
		}

		&send_line ($sock, "DATA\n");
		($code, $text) = &get_line ($sock);
		if ($code != 354)
		{
			warn ("DATA failed: '$code $text'\n");
			return 0;
		}

		while (<MAIL>)
		{
			my $line = $_;
			$line =~ s/^\.$CRLF$/\. $CRLF/;
			$line =~ s/^\.\n$/\. $CRLF/;
			$sock->print ($line);
		}

		close (MAIL);

		$sock->printf ("$CRLF.$CRLF");

		($code, $text) = &get_line ($sock);
		if ($code != 250)
		{
			warn ("DATA not send: '$code $text'\n");
			return 0;
		}
	}

	# Perfect. Everything succeeded!
	return 1;
}

# Get one line of response from the server.
sub get_one_line ($)
{
	my $sock = shift;
	my ($code, $sep, $text) = ($sock->getline() =~ /(\d+)(.)([^\r]*)/);
	my $more;
	$more = ($sep eq "-");
	if ($verbose)
		{ printf ("[%d] '%s'\n", $code, $text); }
	return ($code, $text, $more);
}

# Get concatenated lines of response from the server.
sub get_line ($)
{
	my $sock = shift;
	my ($code, $text, $more) = &get_one_line ($sock);
	while ($more) {
		my ($code2, $line);
		($code2, $line, $more) = &get_one_line ($sock);
		$text .= " $line";
		die ("Error code changed from $code to $code2. That's illegal.\n") if ($code ne $code2);
	}
	return ($code, $text);
}

# Send one line back to the server
sub send_line ($@)
{
	my $socket = shift;
	my @args = @_;

	if ($verbose)
		{ printf ("> "); printf (@args); }
	$args[0] =~ s/\n/$CRLF/g;
	$socket->printf (@args);
}

# Helper function to encode CRAM-MD5 challenge
sub encode_cram_md5 ($$$)
{
	my ($ticket64, $username, $password) = @_;
	my $ticket = decode_base64($ticket64) or
		die ("Unable to decode Base64 encoded string '$ticket64'\n");
	
	print "Decoded CRAM-MD5 challenge: $ticket\n" if ($verbose > 1);
	my $password_md5 = Digest::HMAC_MD5::hmac_md5_hex($ticket, $password);
	return encode_base64 ("$username $password_md5", "");
}

# Store all server's ESMTP features to a hash.
sub say_hello ($$$$)
{
	my ($sock, $ehlo_ok, $hello_host, $featref) = @_;
	my ($feat, $param);
	my $hello_cmd = $ehlo_ok > 0 ? "EHLO" : "HELO";
	
	&send_line ($sock, "$hello_cmd $hello_host\n");
	my ($code, $text, $more) = &get_one_line ($sock);

	if ($code != 250)
	{
		warn ("$hello_cmd failed: '$code $text'\n");
		return 0;
	}
	
	# Empty the hash
	%{$featref} = ();
	
	($feat, $param) = ($text =~ /^(\w+)[= ]*(.*)$/);
	$featref->{$feat} = $param;

	# Load all features presented by the server into the hash
	while ($more == 1)
	{
		($code, $text, $more) = &get_one_line ($sock);
		($feat, $param) = ($text =~ /^(\w+)[= ]*(.*)$/);
		$featref->{$feat} = $param;
	}

	return 1;
}

sub guess_mime_type($)
{
	my $filename = shift;
	if (defined($file_type)) {
		## Use File::Type if possible
		return $file_type->mime_type($filename);
	} else {
		## Module File::Type is not available
		## Still recognise some common extensions
		return "image/jpeg" if ($filename =~ /\.jpe?g/i);
		return "image/gif" if ($filename =~ /\.gif/i);
		return "image/png" if ($filename =~ /\.png/i);
		return "text/plain" if ($filename =~ /\.txt/i);
		return "application/zip" if ($filename =~ /\.zip/i);
		return "application/x-gzip" if ($filename =~ /\.t?gz/i);
		return "application/x-bzip" if ($filename =~ /\.t?bz2?/i);
	}
	return "application/octet-stream";
}

sub basename($)
{
	my $path = shift;
	my @parts = split(/\//, $path);
	return $parts[$#parts];
}

sub prepare_attachment($)
{
	my $attachment = shift;
	my ($path, $mime_type);

	if (-f $attachment) {
		$path = $attachment;
		$mime_type = guess_mime_type($attachment);
	} elsif ($attachment =~ /(.*)@([^@]*)$/ and -f $1) {
		$path = $1;
		$mime_type = $2;
	}
	return ($path, $mime_type);
}

sub attach_attachments($@) 
{
	my $message = shift;
	my @attachments = @_;

	foreach my $attachment (@attachments) {
		my ($path, $mime_type) = prepare_attachment($attachment);
		if (not defined($path)) {
			warn("$attachment: File not found. Ignoring.\n");
			next;
		}
		$message->attach(
			Type => $mime_type,
			Path => $path,
			Id   => basename($path),
		);
	}
}

sub safe_attach($$)
{
	my ($message, $part) = @_;
	## Remove some headers when $part is becoming a subpart of $message
	$part->delete("Date");
	$part->delete("X-Mailer");
	$part->attr("MIME-Version" => undef);
	$message->attach($part);
	return $message;
}

sub mime_message($$)
{
	my ($type, $data) = @_;
	## MIME::Lite doesn't allow setting Type and Data once the 
	## object is created. Well, maybe it does but I don't know how.
	my $message = MIME::Lite->new(
		Type	=> $type,
		Data	=> $data);
	return $message;
}

sub build_message
{
	my ($part_plain, $part_html, $part_body, $message);

	if (@attachments_inline) {
		if (not defined($body_html)) {
			die("Inline attachments (--attach-inline) must be used with --body-html\n");
		}
		$part_html = MIME::Lite->new(Type => 'multipart/related');
		$part_html->attach(Type => 'text/html', Data => $body_html);
		attach_attachments($part_html, @attachments_inline);
		$message = $part_html;
		# undefine $body_html to prevent confusion in the next if()
		undef($body_html);
	}

	if (defined($body_html)) {
		$part_html = MIME::Lite->new(Type => 'text/html', Data => $body_html);
		$message = $part_html;
	}

	if (defined($body_plain)) {
		$part_plain = MIME::Lite->new(Type => "TEXT", Data => $body_plain);
		$message = $part_plain;
	}

	if (defined($part_plain) and defined($part_html)) {
		$part_body = mime_message("multipart/alternative", undef);
		safe_attach($part_body, $part_plain);
		safe_attach($part_body, $part_html);
		$message = $part_body;
	}

	if (@attachments) {
		if (defined($message)) {
			# We already have some plaintext and/or html content built
			# => make it the first part of multipart/mixed
			my $message_body = $message;
			$message = mime_message("multipart/mixed", undef);
			safe_attach($message, $message_body);
			attach_attachments($message, @attachments);
		} elsif ($#attachments == 0) {
			# Only one single attachment - let it be the body
			my ($path, $mime_type) = prepare_attachment($attachments[0]);
			if (not defined($path)) {
				die($attachments[0].": File not found. No other message parts defined. Aborting.\n");
			}
			$message = MIME::Lite->new(
				Type => $mime_type,
				Path => $path);
		} else {
			# Message consisting only of attachments
			$message = mime_message("multipart/mixed", undef);
			attach_attachments($message, @attachments);
		}
	}

	# Last resort - empty plaintext message
	if (!defined($message)) {
		$message = mime_message("TEXT", "");
	}

	$message->replace("From" => $from);
	$message->replace("To" => join(", ", @to));
	$message->replace("Subject" => $subject);
	$message->replace("X-Mailer" => "smtp-cli $version, see http://smtp-cli.logix.cz");
	$message->replace("Message-ID" => time()."-".int(rand(999999))."\@smtp-cli");
	return $message;
}

sub version ()
{
	print "smtp-cli version $version\n";
	exit (0);
}

sub usage ()
{
	printf (
"Simple SMTP client written in Perl that supports advanced
features like STARTTLS and SMTP-AUTH and IPv6. It can also 
create messages from components (files, text snippets) and 
attach files.

Version: smtp-cli v$version

Author: Michal Ludvig <michal\@logix.cz> (c) 2003-2009
        http://smtp-cli.logix.cz

Usage: smtp-cli [--options]

        --host=<hostname>       Host name or address of the SMTP server.
                                (default: localhost)
        --port=<number>         Port where the SMTP server is listening.
                                (default: 25)

        -4 or --ipv4            Use standard IP (IPv4) protocol.
        -6 or --ipv6            Use IPv6 protocol. For hosts that have
                                both IPv6 and IPv4 addresses the IPv6
                                connection is tried first.
        
        --hello-host=<string>   String to use in the EHLO/HELO command.
        --disable-ehlo          Don't use ESMTP EHLO command, only HELO.
        --force-ehlo            Use EHLO even if server doesn't say ESMTP.
        
        Transport encryption (TLS)
        --disable-starttls      Don't use encryption even if the remote 
                                host offers it.
        
        Authentication options (AUTH)
        --user=<username>       Username for SMTP authentication.
        --pass=<password>       Corresponding password.
        --auth-login            Enable only AUTH LOGIN method.
        --auth-plain            Enable only AUTH PLAIN method.
        --auth-cram-md5         Enable only AUTH CRAM-MD5 method.
        --auth                  Enable all supported methods. This is 
                                normally not needed, --user enables 
                                everything as well.

        Sender / recipient
        --from=<address>        Address to use in MAIL FROM command.
        --to=<address>          Address to use in RCPT TO command. Can be 
                                used multiple times.

        Send a complete RFC822-compliant email message:
        --data=<filename>       Name of file to send after DATA command.
                                With \"--data=-\" the script will read 
                                standard input (useful e.g. for pipes).

        Alternatively build email a message from provided components:
        --subject=<subject>     Subject of the message
        --body-plain=<text|filename>
        --body-html=<text|filename>
                                Plaintext and/or HTML body of the message
                                If both are provided the message is sent
                                as multipart.
        --attach=<filename>[\@<MIME/Type>]
                                Attach a given filename. 
                                MIME-Type of the attachment is guessed 
                                by default guessed but can optionally
                                be specified after '\@' delimiter.
                                For instance: --attach mail.log\@text/plain
                                Parameter can be used multiple times.
        --attach-inline=<filename>[\@<MIME/Type>]
                                Attach a given filename (typically a picture)
                                as a 'related' part to the above 'body-html'. 
                                Refer to these pictures as <img src='cid:filename'>
                                in the 'body-html' contents.
                                See --attach for details about MIME-Type.
                                Can be used multiple times.
        --print-only            Dump the composed MIME message to standard
                                output. This is useful mainly for debugging
                                or in the case you need to run the message
                                through some filter before sending.

        Other options
        --verbose[=<number>]    Be more verbose, print the SMTP session.
        --missing-modules-ok    Don't complain about missing optional modules.
        --version               Print: smtp-cli version $version
        --help                  Guess what is this option for ;-)
");
	exit (0);
}