We have a seperate forest with user-accounts. And another forest with the Exchange mailboxes. When accessing OWA using credentials from the Exchange forest, the mailbox opens just fine. But when using credentials from the user-forest, there is an error. Using Outlook to access the same mailbox works fine, since we have supplied permissions to the resource-mailbox through a Trust. So how to fool OWA to open the right mailbox with external credentials ? Is converting the resource-mailbox to a Linked-Mailbox the only option I have ? I already know I can 'force' OWA to open the right mailbox if I add the primary SMTP address to the owa-URL. But users will not understand or want that. Grtz Richard

Hi Resource mailbox accounts will be disabled by default, what is the credential you are passing to open the resource mailbox in owa?. if you dont want the option tp pass the email address in URL. Login to the mailbox which is having full access rights and at the right corner, there will be one option to show whose mailbox you logged in, there will be drop down to access other mailbox. Enter the display name of the mailbox you want to access - if you have enough permission, that mailbox will be opened in other window. I'f Im wrong, inform your issue in detail.