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Step 1 - Click 'New Email'
Step 2 - Click the 'From' drop-down menu to select , then select 'Other Email Address...'
Step 3 - Type the name of the Shared Exchange Mailbox nameinto the dialog box, then click OK
Step 3 4 - Verify the The Shared Exchange Mailbox name populates will now populate in the 'From' dialog boxfield
Step 5 - The mailbox name will also be available to select from the drop-down menu
Step 6 - Finish typing your message, and then choose Send.