Attachment

Hi,
I would like add an attachment from external source to a mail.

So, I've the path of the file that i want Attach, so how I can attach it without using file browser.
Exists a method like Msg.addAttachment(path-of-the-file)?

I've a ZmMailApp object, but I don't know what is the method to modify the attachment list.

Please, every answer is welcome

Thank's