I don't believe this is true. The attachment never gets downloaded
independently of the remainder of the mesage body, since the attachment is
PART of the message body. If you can see the message in the preview pane,
the attachment HAS been downloaded. This would be true for ANY mail client
that allows you to see the message body. Outlook 2003's behavior is to
write the attachment to the secure temp folder if you open it from within
the message.
the behaviour I am observing in Outlook 2003 (with Cached Exchange
Mode on) with additional mailbox:
In the additional mailbox:
When I single-click on a message, I see a preview in the Preview Pane.
Nothing is downloaded to the securetemp folder (except a gif or bmp,
if the message has an embedded image). The attachment (in this case, a
Word document), is not downloaded to securetemp.
When I double-click the message, same behaviour. When I double-click
the attachment and open it, it is at that point that the attachment is
written to secure temp.
I will test the above with Outlook 2007 and report.
The above is the behaviour that I want with the additional mailbox,
especially in Outlook 2007.