Messaging Attachments - Read Only?

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Hi...I'm hoping someone has experienced this and has an answer...the vendor wasn't too helpful...then again it was probably their 1st level support...

I just got a Sprint HTC Touch Pro and was playing with ListPro v5 software. I like that I can email a list to someone else with a WM device, however when they open the .clf file as an attachment, it opens, but only in Read Only mode, which doesn't allow checking items off, only viewing the list.

Ideally, I'd like to email a grocery list to someone and have them simply open the attachment and be able to check things off without having to save the attachment, etc. Is this just the way Windows Mobile is or is there a registry hack available? Outlook on the desktop operates like this too in reading pane mode, but if you open the message in a new window and click the attachment it is in read-write mode.

Anyone know how to make what I'm looking to do work?

Thanks in advance to any gurus with the answer!