Do Outlook client cache X500 address or legacyExchangeDN values or both ?

I saw some article regarding X500 address caching function of Outlook.

But I wounder Outlook cache X500 address or legacyExchangeDN values or both.

Do Outlook client cache X500 address or legacyExchangeDN values or both ?

Because we use MIIS for galsync and contact objects and mailbox proxyaddresses have multiple X500 addresses which is not own ExchOrg's X500 address.