PHPMailer Mini is a simple-to-use replacement for PHP mail(). It is a single file with no dependencies and a very small footprint (around 21 Kb) and supports:

• Text and HTML
• HTML can contain base64 images as well as any valid HTML tags
• Attachments of any type (files or images)
  note: inline "attachments" are not supported (only base64 images)

PHPMailer Mini is designed to support only Sendmail ( directly or by using PHP mail() ). If you require IMAP or SMTP use PHPMailer Pro or PHPMailer Lite.

Really simple to use, here's an example:

$mail = new PHPMailerMini();
$mail->SetSender(['yourname@example.com'=>'Sender Name']);
$mail->AddRecipient(['recipient@example.net'=>'Recipient Name']);
$mail->SetSubject("PHPMailer Mini Sendmail minimal test");
$mail->messageHTML  = "<p>Test HTML message, minimal configuration.</p>";
$mail();

PHPMailer Mini supports PHP7.4 (and up) and is licensed under MIT).