Exchange 2007 > 2013 Transition/Migration, POPUP on Outlook 2010 or Public Folder can't be open from 2007
Error1: When you click a Public Folder which lies on 2007 in Outlook.exe
"Cannot expand the folder. Microsoft Exchange is not available. Either there are network problems or the Exchange server is down for maintenance."
Event 401 is logged in IIS log file on 2007 side
Error2: Even if you have selected the option not to DOWNLOAD and other resources or public folder you Recieve constant authentication POPUPS "Windows Security" with username password. Outlook.exe shows password need at some point. Even if you chose remember my Credentials.
You have to change the Authentication for "Outlook Anywhere" on old 2007 side to NTLM.
A general reason is that Exchange 2013 works OVER "Outlook Anywhere" all the time. To make it correct you could enable "Outlook anywhere" backwards/afterwards on the old Exchange 2007. Warning: However this function will run from 10-60 Minutes depending on your Exchange 2007. Read and search more if it not enabled on the old Exchange 2007 and you want to do that while the old 2007 is productive. Most blogs don't mention that and most of them do 2007>2010>2013 and some 2007>2013 direct. However they assume you have "Outlook anywhere" on 2007 already on before you begin the swing Transition (Migration).
Exchange 2007 and 2013 Coexistence:
Check Logfiles on Exchange 2007 under:
Search for string "/rpc/rpcproxy.dll"
This is the Health check the Exchange 2013 does:
RPC_IN_DATA /rpc/rpcproxy.dll - 443 - 192.168.20.198 HttpProxy.ClientAccessServer2010Ping
401 2 5 0
Controll the Settings on the Exchange 2007.
get-OutlookAnywhere -Server "servername2007" | fl identity, IISAuthenticationMethods
Set-OutlookAnywhere -Identity " servername2007\Rpc (Default Web Site)" -IISAuthenticationMethods Ntlm
Or in GUI on the Exchange 2007
Do an IISRESET
If that does not work > Also recycle the IIS folders and Reboot the 2007.
Open IIS Konsole
Go to "Application Pools"
IIS Logfile after the change should be with a 500 value.
2016-04-26 14:20:35 192.168.20.13 RPC_IN_DATA /rpc/rpcproxy.dll - 443 - 192.168.20.198 HttpProxy.ClientAccessServer2010Ping 500 0 64 45021
Change on client side
IF account still under 2007 and using ONLY Outlook Anywhere you then have to change something in outlook.exe on each client THAT is laptop or workgroup and not domain joined. If Autodiscover and the EXPR-Record are correct this should work by itself.