If you're using cached Exchange mode and you have the account set up to
download headers and text in the Send/Receive group, Outlook will download
the message in its entirety when viewed in the Reading Pane. Attachments
are part of the body of the message. If you download the message, you
download the attachments.
--
Brian Tillman [MVP-Outlook]

thanks. Doesn't quite answer my question. My primary mailbox is Cached
Exchange Mode. I have an additional mailbox which isn't cached
(because additional mailboxes can't be cached). So I guess the
additonal mailbox is in "online" mode. The problem is, in the
additional mailbox, when I single-click on a message to view it in the
Preview Pane, there is a long delay as though Outlook is downloading
the text and attachment. The delay *only* occurs for messages with
large attachments, which is why I suspect that Outlook 2007 is at
fault.

The behaviour I would expect is (in the additonal mailbox), I single-
click on a message to view it in the Preview Pane and the body of the
message is downloaded. To download the attachment, I would double-
click them.

I hope this explanation makes sense.