Cannot open a hyperlink in an email written with OL 2007 in OL 200

Hi I have a strange problem.

We are using RTF format in Outlook 2003, deactivating word as Email editor.
This enables to send hyperlinks to files on network shares (e.g.
X:\Marketing\letter.doc) by using Insert File then choosing Insert as
Hyperlink. This appears as <file://\\server\share\Marketing\letter.doc> in
the email body and is clickable.
The same email sent to an Outlook 2007 also works, e.g. it's possible to
click on the hyperlink.

Now an email with a hyperlink written with Outlook 2007 will work when read
in Outllok 2007. I also note that is is transformed on the fly as a hyperlink
with text X:\Marketing\letter.doc and link
File:///\\server\share\Marketing\letter.doc, although I deactivated the
option 'Replace Internet and Network Paths with hyperlinks' in both
AutoFormat and AutoFormat as you type in Both Outlook's Editor options as
well as in Word 2007.

When read with Outlook 2003, unfortunately the hyperlink is not there
anymore, only text (e.g. X:\Marketing\Brief.doc) and people cannot click on
the hyperlink.

Any idea how I can make these hyperlinks written in Outlook 2007 work with
Outlook 2003?

Thanks,
Cedric