To avoid problems of character encoding in sending emails using the class PHPMailer we can configure it to send it with UTF-8 character encoding using the "CharSet" parameter, as we can see in the following Php code:
$mail = new PHPMailer();
$mail->From = '[email protected]';
$mail->FromName = 'Mi nombre';
$mail->AddAddress('[email protected]');
$mail->Subject = 'Prueba';
$mail->Body = '';
$mail->IsHTML(true);
// Active condition utf-8
$mail->CharSet = 'UTF-8';
// Send mail
$mail->Send();