netsmtp-settings.php

$conf['mail_system'] = ['default-system' => 'NetSmtp_MailSystemProxy'];
$conf['netsmtp_proxy'] = ['default' => 'MimeMailSystem'];
$conf['netsmtp_catch'] = [
  '[email protected]',
  '[email protected]',
  // ...
];
$conf['netsmtp_debug_trace'] = true;
$conf['netsmtp_debug_mime'] = true;
$conf['netsmtp'] = [
  'default' => [
    'hostname'  => 'smtp.example.com',
    'port'      => 465,
    'use_ssl'   => true,
    'username'  => 'someone',
    'password'  => 'secret',
  ],
];