Norton Anti-Spam does not work when Outlook Express is first started after boot-up

[Mortimer]

A customer with Norton Internet Security 2007 and the add-on package for
anti-spam is reporting a very strange symptom.

When he boots the PC at the beginning of each day and opens Outlook Express,
none of the spam messages on his POP server are put in the Norton Anti-Spam
folder: all go into his Inbox.

However if he then does a Send/Receive at various times during the day
(without rebooting the PC and without stopping and restarting OE) then most
spam is put into the AntiSpam folder, as they should be.

OE is set up check for new messages every 30 minutes. "Check for new
messages at startup" is turned on, although he has also experimented with
turning that option off.

Can anyone think of an explanation for this different behaviour: that the
first check for email after booting up and starting OE causes Norton to fail
to classify spam, but subsequent checks for email allow it to work OK. This
is 100% reproduceable.

He thinks that the symptom dates from when he upgraded from dial-up to
broadband via a router.