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If you have multiple accounts in Mail for Windows 10, you can link those accounts so that all of your emails appear in one inbox.
Link multiple inboxes
You can link any of your inboxes. Any unlinked inboxes will remain separate. If you have five accounts and link four of them, the fifth account will remain separate.
Choose Settings > Manage Accounts > Link inboxes.
Give your linked inbox a name. If you want to link all of your available inboxes, choose Save. If you don't want to link a particular account, uncheck the box next to that account and then choose Save.