Policy
Return e-mail alias if it exactly matches the provided e-mail address when searching OAB
By default, when searching the Offline Address Book, Outlook resolves e-mail addresses using Ambiguous Name Resolution. With Ambiguous Name Resolution, Outlook suggests additional possible matches (if they exist) even if there is a name that matches exactly the e-mail alias entered. By enabling this setting, you can change the behavior so that Outlook returns a single e-mail address if it exactly matches an e-mail alias.
d6a2291f4a45 L_OfflineAddressBookexactaliasmatching Registry
Copy registry mappings
HKCU\software\policies\microsoft\exchange\exchange provider\oab exact alias match (enabled) = 1
HKCU\software\policies\microsoft\exchange\exchange provider\oab exact alias match (disabled) = 0Policy notes
By default, when searching the Offline Address Book, Outlook resolves e-mail addresses using Ambiguous Name Resolution. With Ambiguous Name Resolution, Outlook suggests additional possible matches (if they exist) even if there is a name that matches exactly the e-mail alias entered. By enabling this setting, you can change the behavior so that Outlook returns a single e-mail address if it exactly matches an e-mail alias.