For my use-case, I’ve never had easy access to a private/internal mail server. I’ve always used SMTP methods to connect to gmail or yahoo. I haven’t ever tried any of the other solutions (MailTools, Mail::Sendmail), so I don’t know if they work for my scenario. It does look like as of now (Feb 2019), MIME::Lite and Mail::Sender are not recommended by their respective maintainers.

• MIME::Entity is used to construct a message with/without attachments.
• Email::Sender::Simple is used to actually send the message using a variety of transports.
• Email::Sender::Transport::SMTP is used to log into my gmail account.

I’ve tested this on gmail and yahoo. For gmail, I had to go into my account settings and allow less secure apps to access my account. I think this just refers OAuth. You will still use TLS/SSL to talk to Gmail, so you won't be sending your plaintext password over the Internet.

use MIME::Entity;
use Email::Sender::Simple qw( sendmail );
use Email::Sender::Transport::SMTP;

$user = "myself\@gmail.com";
#must be a legitimate email account
$pass = "mypassword";
$mailhost = "smtp.gmail.com";
#for yahoo, use smtp.mail.yahoo.com

$rcpt = other.user@other.com;
#could also send it back to myself;
$file = "my_picture.jpg";
$debug = 0; #enable by setting to 1

my $transport = Email::Sender::Transport::SMTP->new(
  host => $mailhost,
  port => 465,
  ssl => "ssl",
  sasl_username => $user,
  sasl_password => $pass,
  debug => $debug
  );

my $mime = MIME::Entity->build(
  To => $rcpt,
  From => $user,
  Subject => "Simple MIME from Perl",
  Type => "multipart/mixed");

$mime->attach(Data => "Hungry? Eat a Milky Way",
  Type => "text/plain");
if(defined $file and -e $file)
{
  $mime->attach(Path => $file,
      Encoding => "base64",
      Disposition => "attachment");
}

sendmail($mime, { transport => $transport });
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