post-by-email: shortcodes not working

Hi,

The shortcodes in ‘Post-by-email’ are not working for me. When I send an email containing [tags x,y,z] in the body of the email, the post appears on my blog with the text [tags x,y,z] instead of being tagged with the tags x,y and z.

I am following the Codex info on this page here. What should I do so that the shortcodes work? I’d appreciate any help you can provide. Thanks.

Supporting info:
Wordpress installed offline on a Mac OS X 10.4
Client from which email is sent: Gmail or Hotmail
Client to which email is sent: Gmail