Automapping is enabled by default, but it can be disabled by running the following cmdlet:
Add-MailboxPermission TeamMailbox -User kmeyer -AccessRights FullAccess -AutoMapping $falseThe cmdlet above gives user Ken Meyer full access to the TeamMailbox mailbox and disables automapping for that mailbox.
I published the Enable-AutomappingForFullAccessMailboxes.ps1 script for Exchange in the Microsoft Script Center Gallery. The script re-enables Outlook automapping on mailboxes where users have been given full access rights. It runs on Exchange 2010-2019 and Exchange Online, and must be run from the Exchange Management Shell (EMS).