Here is a working example of how to send multipart mail messages using Net::SMTP. Code for sending plain text, a plain text file, and a binary image (jpg) are provided.

Hope this helps!

#!/usr/bin/perl

use Net::SMTP;
use strict;
use warnings;

use MIME::Base64 qw( encode_base64 );
#use MIME::Base64 qw( decode_base64 );

my $from = 'from@email.com';
my $to = 'to@email.com';

my $attachBinaryFile= 'test.jpg';
my $attachTextFile = 'test.txt';

my $boundary = 'frontier';

open(DAT, $attachTextFile) || die("Could not open text file!");
my @textFile = <DAT>;
close(DAT);

my $smtp = Net::SMTP->new('your.smtp.com', Timeout => 60) || die("Coul
+d not create SMTP object.");
print "Sending mail\n";
$smtp->mail($from);
$smtp->recipient($to, { SkipBad => 1 });
$smtp->data();
$smtp->datasend("To: $to\n");
$smtp->datasend("From: $from\n");
$smtp->datasend("Subject: Multi part test\n");
$smtp->datasend("MIME-Version: 1.0\n");
$smtp->datasend("Content-type: multipart/mixed;\n\tboundary=\"$boundar
+y\"\n");
$smtp->datasend("\n");
$smtp->datasend("--$boundary\n");
$smtp->datasend("Content-type: text/plain\n");
$smtp->datasend("Content-Disposition: quoted-printable\n");
$smtp->datasend("\nToday\'s files are attached:\n");
$smtp->datasend("\nHave a nice day! :)\n");
$smtp->datasend("--$boundary\n");
$smtp->datasend("Content-Type: application/text; name=\"$attachTextFil
+e\"\n");
$smtp->datasend("Content-Disposition: attachment; filename=\"$attachTe
+xtFile\"\n");
$smtp->datasend("\n");
$smtp->datasend("@textFile\n");
$smtp->datasend("--$boundary\n");
$smtp->datasend("Content-Type: image/jpeg; name=\"$attachBinaryFile\"\
+n");
$smtp->datasend("Content-Transfer-Encoding: base64\n");
$smtp->datasend("Content-Disposition: attachment; filename=\"$attachBi
+naryFile\"\n");
$smtp->datasend("\n");
my $buf;
open(DAT, "../uploads/$attachBinaryFile") || die("Could not open binar
+y file!");
   binmode(DAT);
   local $/=undef;
   while (read(DAT, my $picture, 4096)) {
      $buf = &encode_base64( $picture );
      $smtp->datasend($buf);
   }
close(DAT);
$smtp->datasend("\n");
$smtp->datasend("--$boundary\n");
$smtp->dataend();
$smtp->quit;
print "Mail sent\n";
exit;
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