This can also be caused by a missing entry in the LDT (Local Domain Table) on the ISA Server (if you have one). The local domain (AD DomainName) has to be in the LDT or Exchange cannot find the Outlook client to send the UDP notification to.
The LDP entry should look something like...
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.