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✏️ Editing: 6.A.smtp-verify

#!/usr/bin/perl -w
#	Here's something that is of actual use, and should be relatively
#portable.
#	Given an email address and a mail server name check to see if
#the address is deliverable on that box. This can be used for address
#verification or spam relay checking.
#
#	The point of this is to show how you can take a generic handle
#and interact with it. In this example a socket is used.

use Expect;
use IO::Socket;

# $Expect::Debug=1
# $Expect::Exp_Internal=1;
# $Expect::Log_Stdout=0; # On by default. This does not affect Expect
# objects created with Expect->exp_init() however. By default the output of
# those handles will not be output to the screen. use $handle->log_stdout(1)
# to turn that on after you initialize the handle.

# Arg. 0 hostname of mail server
$mail_server=shift(@ARGV);
# Remaining args will be email addresses.
@addresses=@ARGV;
die "Usage: $0 mail_server address1 [address2 address3.. addressN]\n" unless
  @addresses;

# Connect to mail server. This is right out of perldoc IO::Socket.
$smtp_sock = IO::Socket::INET->new(PeerAddr => "$mail_server:smtp(25)");
die "Couldn't connect to $mail_server, $!" unless defined $smtp_sock;

# Turn the socket in to an expect object.
$smtp_session=Expect->exp_init($smtp_sock);
# By default Expect doesn't print out the output of an exp_inited item.
# Generally you don't want handles jabbering at you. In this case
# we might turn it on so we can watch what happens.
#$smtp_session->log_stdout(1);

# Watch debugging?
#$smtp_session->exp_internal(1);

# Ok, now let's see if the mail server wants to talk to us:
$smtp_session->expect(30,'-re','^220.*\n')||die "Bad response from server\n";

# Cool. Now let's introduce ourselves to the server.
# There are many other ways to gain the FQDN of this box. This is mine,
# and it's easy. This of course assumes you have uname and that -n returns
# your hostname.
$my_hostname = `uname -n`; chomp $my_hostname;

print $smtp_session "HELO $my_hostname\n";

# My server responds with a 250 + stuff. Presumably that's RFC compliant.
# Feel free to go look :-)
$smtp_session->expect(30,'-re','^250.*\n')||die "Bad response after HELO\n";

# Try sending mail.. I should probably use my username rather than user@
# but I'm too lazy.
print $smtp_session "MAIL FROM:<user\@$my_hostname>\n";
$smtp_session->expect(30,'-re','^250.*\n')||die "Bad response after FROM\n";

# Now to check each address...
foreach $address (@addresses) {
  print $smtp_session "RCPT TO:<$address>\n";
  # Now check the status...
  ($match_num,$error,$match)=$smtp_session->expect(30,'-re','^\d\d\d');
  die "Never got response back after trying RCPT to $address\n" if $error;
  $status = $match;
  # Read to the newline so the server will be ready for the next address.
  # If the server spit back something other than 250 we'll display the 
  # Whole error.
  ($match_num,$error,$match)=$smtp_session->expect(30,'-re','.*\n');
  die "Server seems to have hung after trying address $address\n" if $error;
  if ($status == 250) {
    $status = "ok\n";
  } else {
    $status.=$match;
  }
  print "Status of address $address: $status";
}

# Be good citizens, send a quit.
print $smtp_session "QUIT\n";

# At which point it should die nicely.
$smtp_session->soft_close();

MR SKB