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Signing your email messages with a digital ID helps to prove your identity and prevent message tampering.

Certificate authority (CA) A certificate authority is an entity similar to a notary public. It issues digital certificates, signs certificates to verify their validity and tracks which certificates have been revoked or have expired. Top of Page Digital signature assurances The following terms and definitions show what assurances are provided by digital signatures. Authenticity The signer is ...

瞭解如何在行動裝置、Windows 裝置或 Xbox 主機上兌換 Microsoft/Xbox 禮品卡或其他代碼。

Find out how to submit a request for a refund for a purchase of digital Xbox content.

Hotmail is now Outlook.com To sign in to Hotmail, you'll need your Microsoft account username and password. Sign in at outlook.live.com

Need help with an Xbox console, an Xbox game, or Xbox network? Find out how to get in touch with us.

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How to create or edit your Outlook signature for email messages. Include your signature, text, images, electronic business card, and logo.

Learn how to protect your PC, identity, and data from tech support scams.