I've read this thread. ********************************** My scenario 2 sites W2K3 boxes DCs/GCs2x Exchange 2K3 STDnative modeHi all,I've got a pretty anoying problem. On site2 I have an Exch2. When setting up users on Outlook 2007 I keep getting an authentication popup (problem with Kerberos I understand). I found a workaround by enforcing NTLM, which I do not want to roll out. Basically when I ran from support tools prompt:setspn -L Exch2 --> I do not get an entry for exchangeAB to the local site2 Global Catalog serversetspn -L Exch1 --> I do get an entry for exchangeAB to the local site1 GC server.Therefore i believe the problem lies here, where Exch2 isn't "talking" to GC for authentication. I've now run: setspn -A exchangeAB/site2GC site2GC setspn -A exchangeAB/site2GC.mydomain.com site2GC Then when I run: setspn -L Exch2 I still do not get any entries for Exch2 Can anyone help?