MAIL -> booleandelattach ( [ string name ] )
Return TRUE if has been successfully deleted, FALSE if not.
By default, all attachments will be deleted if the parameter name it's not provided.
Example:
$m = new MAIL;
// add attachment
$m->Attach('text content', 'text/plain', 'filename.txt');
// delete attachment
$m->DelAttach('filename.txt');
// delete all attachments
$m->DelAttach();