1. Turn off 2FA .
2. on 'https://myaccount.google.com/security?pli=1#connectedapps', look for and allow Less secure app access
3. on 'https://myaccount.google.com/lesssecureapps', same thing.
4. use the slightly elaborated perl program:

#!/usr/bin/env perl
use strict;
use warnings;
use autodie;
use Data::Dumper;

my $gauthtxt= "gauth.txt";  # can define default sending user account 
+and password
    ## format: 'user\temail\npasswd\tstring\n'

################################################################
# parse inputs

# defaults
my %smtp= ( server => 'smtp.gmail.com', port => '587', subject => "tes
+ting gmailer.pl", body => "gmail-tester $0: ".localtime() );

# more defaults in gauth.txt
if (-e $gauthtxt) {
  print STDERR "[reading $gauthtxt]\n";
  open(my $GA, "<", $gauthtxt);
  while (<$GA>) {
    chomp; (/^([a-z]+)\s+(.*)$/) or die "line in $gauthtxt is not pars
+eable: $_\n";
    $smtp{$1}= $2;
  }
  close($GA);
}

# command line arguments
foreach (@ARGV) {
  foreach my $keyword (qw(user to passwd subject body)) { (/^$keyword=
+(.*)/) and $smtp{$keyword}=$1; }
}

(exists{$smtp{from})) and $smtp{user}=$smtp{from}; ## special equivale
+nce

################################################################
# check inputs

foreach (qw(user to passwd subject body)) {
  exists($smtp{$_}) or die "'$_' needs to be in $gauthtxt or spcified 
+on command line with '$_=...'\n";
}


use Email::Valid;
(Email::Valid->address($smtp{user})) or die "your own user account $sm
+tp{user} is not a valid email address";
(Email::Valid->address($smtp{to})) or die "your recipientd account $sm
+tp{to} is not a valid email address";


################################################################
# send email

use Email::Sender::Simple qw(sendmail);
use Email::Sender::Transport::SMTPS ();
use Email::Simple ();
use Email::Simple::Creator ();


my $transport = Email::Sender::Transport::SMTPS->new({
  host => $smtp{server},
  port => $smtp{port},
  ssl => "starttls",
  sasl_username => $smtp{user},
  sasl_password => $smtp{passwd},
});

my $email = Email::Simple->create(
  header => [
    To      => $smtp{to},
    From    => $smtp{user},
    Subject => $smtp{subject}
  ],
  body => $smtp{body}."\n",
);

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

print "\nemail sent from $smtp{user} to $smtp{to}.\n";
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