Cross Domain Availability Service

How to publish free/busy information between 2 domains (without trusts) using Exchange 2007.

List of prerequisites:

1. An account on each domain that can be used to access the free/busy information.

Create a new account on each domain. This account should have minimal privileges and should not have a mailbox.

2. Ability to resolve the autodiscover address. e.g. autodiscover.domain.com

Each client wishing to access the free/busy information of a remote user, must be able to resolve the autodiscover address of the remote users domain.

You can test this by using Outlook 2007's "Test E-mail AutoConfiguration" tool. Found by Ctrl + Right clicking the Outlook task bar icon (you will need credentials for the remote domain).

Microsoft article describing how autodiscover works: http://technet.microsoft.com/en-us/library/bb232838.aspx

Microsoft article describing how to configure autodiscover: http://technet.microsoft.com/en-us/library/bb201695.aspx

3. A contact in your GAL (global address list) for the remote user.

You will need a contact in the GAL for every remote user whose free/busy information you wish to see.

How to configure exchange:

All exchange tasks are performed using Exchange Management Shell.

1. Firstly you will need to set your new local domain account (that you created in step 1) to have privileges to see all free/busy information on your domain. This will need to be done for both domains if you wish the sharing of free/busy information to go both ways.

On Exchange 2007 server in Domain 1
set-availabilityconfig -orgwideaccount "domain1.local\domain1fbacct"

On Exchange 2007 server in Domain 2
set-availabilityconfig -orgwideaccount "domain2.local\domain2fbacct"

2. Secondly you will need to add the remote domain as an Availability Address Space on both domains, specifying the local domain account of the remote domain as used above.

On Exchange 2007 server in Domain 1
$a = get-credential
/// This opens a credentials prompt, Enter in domain2\domain2fbacct
Add-AvailabilityAddressSpace -ForestName domain2.com -AccessMethod OrgWideFB -Credential $a

On Exchange 2007 server in Domain 2
$a = get-credential
/// This opens a credentials prompt, Enter in domain1\domain1fbacct
Add-AvailabilityAddressSpace -ForestName domain1.com -AccessMethod OrgWideFB -Credential $a

Overview:

Basically, what we have done is given a local account on each domain privileges to access local free/busy information. Then on the remote domain configured an availability address space for the remote domain using the account that we have given free/busy privileges too.

How to use:

This works in both Outlook 2007 and Outlook Web Access.

• Create a new meeting request/appointment.
• Click on Scheduling Assistant
• Add the remote attendees from your GAL
• Wait for the free/busy information to be populated.

More resources:

Microsoft guide on how to configure the Cross domain availability service for Cross-Forest topologies
Client Access Server Role: Overview
How to Diagnose Availability Service Issues