ISA 2004/OWA/redirect log on page

Hi,

We use ISA Server 2004 to publish Outlook Web Access of Exchange Server 2003 with Form based authentication. Sometimes, our Exchange Server is offline while we apply operating system updates or Exchange specific hotfixes.

If a user tries to log on to Outlook Web Access while the Exchange Server is offline, he or she gets an error message stating that the Exchange Server can’t be reached. That message appears after the user pressed the Log On Button as the Logon mask is provided by ISA Server.

Although we announce those maintenance works, people often call help desk why they can’t logon to Outlook Web Access.

Is it possible to temporary redirect the OWA page to a static page announcing the maintenance works without time consuming modifying the ISA Server rules?

--
Kind regards,
Dominik
.