Undefined variable $filetype. Wrong variable name used in smtp_drupal_mail_wrapper. Should be $file_type

Database: MySQL 5.1.33
Web Server: Apache 2.2.11
PHP 5.2.9
Drupal 6.22
SMTP version 6.x-1.0

Trying to add an attachment to an email the Content-Type is set to text/plain.

I think it depends on the call to the $mail->AddAttachment() with a variable that does not exist ($filetype instead of $file_type) in smtp_drupal_mail_wrapper function (line 727 of smtp.module)

A similar problem was found (and solved) in the D7 version (http://drupal.org/node/1816092)