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If you accidentally marked all the inbox emails as Phishing in Outlook, it will be moved to the Junk or SPAM email folders.
To revert the changes, open the Junk e-mail folder and select the emails you want to move back to the inbox. Once selected, right-click and select Move to inbox. Or select Report > Not junk.
If you are having trouble selecting each email individually, you can click the select all option and then move all of them to your inbox.
In addition, go to Outlook email settings > Mail > Junk email > Blocked Senders and domains.
If you see any email address you want to receive emails from, remove it from the lists.