HiWe are running Exchange 2007 SP1 and Outlook 2007 SP2.We have a sister company where some of our users are located. There is a VPN between the sister company and us, but they use a seperate AD forest/Exchange org etc.The way our users over there are set up is for them to log onto the sister company's AD forest (they have accounts in that forest), but then their Outlook is connected to our Exchange server (not via Outlook Anywhere, but MAPI since there is a VPN connection). They are prompted for credentials to authenticate to our Exch server when they connect.This all works fine, however this morning users in the sister site are complaining that they cannot see other people's Free Busy. Users in the main site are unaffected.The users in the remote site can access the Availability URL fine, so I'm confused what could be causing this?

Joe,Let them try the auto configure e-mail option from Outlook to check if they retrieve the correct configuration.Regards,JohanExchange-blog: www.johanveldhuis.nl

Hi GuysSo - to confirm - the users are at a sister site (logged onto the sister AD forest), but their Outlook is configured to point to our Exchange servers.Regarding Autodiscover - how would the Outlook client know to look for our Availability service URL and not the one at the sister site? Since they are using the sister company's DNS, AD etc, wouldn't their Outlook be pointed to there? Or would the DSProxy return a DC local to our Exchange server for these lookups?

There are a number of special considerations to publish Free/Busy in cross-forest scenarios. Can you confirm that you've followed these steps: http://technet.microsoft.com/en-us/library/bb125182(EXCHG.80).aspx

Thanks Neil.But we do not want our users over there to see the Free/Busy info of the partner user's site - so there is no cross-forest scenario here, I think?More so, I'm wondering how Outlook initially connected to our Availability service - how does it know to connect to our service and not the one that is used at the Partner site? I figured out the problem - the Partner site had made a change to DNS and deleted the entry for our CAS server, but I'm wondering how Outlook knows that it should connect to our Availability service when the client itself (i.e. the PC/laptop) is part of a different domain?How does this work in DNS?

I see, these are users with linked accounts in a separate forest. You are not sharing information between the Exchange orgs. Then yes the link I provided does not help. At any rate, you should have an A record in DNS for autodiscover.yourdomain.com, where yourdomain.com is the email domain you are using. If they are using your partners DNS system, I would confirm with them that they get a valid answer for autodiscover.yourdomain.com and can contact the server. They can validate the configuration via the "Test E-Mail Autoconfiguration" option which is available by right-clicking on the Outlook icon in the notification area. This tool produces a log file which includes endpoints for the availability service and OAB URL. Edit: Based on your post describing that they deleted the CAS server A record, I imagine they are also missing the autodiscover record as well. This can also be a CNAME to your CAS server.