In a previous article I explained how to install and configure the auto accept agent (for exchange 2003)
Now, you have migrated your users from 2003 to Exchange 2010.
Some of your users was configured with Auto Accept Agent.
You want those users do the same they do in Exchange 2003.
1) Set the attribute IsResource for these users
In Exchange Management Shell, type:
Get-Mailbox -Identity YourMailBox | ft Name, IsResource
If result in IsResource will be FALSE then convert this mailbox with second command:
Set-Mailbox -Identity YourMailBox-Type Room
2) Activate the Resource Booking Attendant on the MailBox
In Exchange Management Console > Recipient Configuration > Mailbox > Properties
You can see now new Resource tabs have appeared.
Hit on Resource General and check "Enable the Resource Booking Attendant..."
Hit on Resource Information Tab and configure as you want.