Archive Shuttle follows steps below to assign an owner to SourceOne archive
1. If there is still Exchange on-prem mailbox then Archive Shuttle matches it with EmailAddress in dbo.SourceOneArchive table and LegacyExchangeDN in dbo.ExchangeMailbox table and UserSID in dbo.User
2. If there is only Office 365 mailbox then Archive Shuttle tries to match owner with SourceOne archive using Address in dbo.UserProxyAddress and EmailAddress in dbo.SourceOneArchive
dbo.ExchangeMailbox and dbo.UserProxyAddress table is populated during AD sync.
dbo.SourceOneArchive archive is populated during Archive Collection.