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 It issues digital certificates, signs certificates to verify their validity and tracks which certificates have been revoked or have expired.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 ...

Find solutions for Xbox account and profile issues, manage settings, and get support for your Xbox experience.

了解如何在您的行動裝置、Windows 裝置或 Xbox 主機上兌換 Microsoft/Xbox 禮品卡或其他優惠碼或優惠。

Learn how to redeem Xbox prepaid codes for games, subscriptions, and digital content, and enjoy endless surprises with your Xbox account.

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

連絡 Microsoft 支援服務。尋找常見問題的解決方案，或向支援專員尋求協助。

Microsoft prioritizes account security and works to prevent people from signing in without your permission. When we notice a sign-in attempt from a new location or device, we help protect the account by sending you an email message and an SMS alert. If your phone number or email changes, it's important to promptly update the security contact info on the Security basics page so we can work with ...

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Protect yourself from phishing Phishing (pronounced: fishing) is an attack that attempts to steal your money, or your identity, by getting you to reveal personal information -- such as credit card numbers, bank information, or passwords -- on websites that pretend to be legitimate. Cybercriminals typically pretend to be reputable companies, friends, or acquaintances in a fake message, which ...

Contact Microsoft Support. Find solutions to common problems, or get help from a support agent.