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 It issues digital certificates, signs certificates to verify their validity and tracks which certificates have been revoked or have expired.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

Xbox Support 提供有关 Xbox、Game Pass 和账单问题的帮助，并通过社区提供建议和客户服务。

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

Microsoft Support is here to help you with Microsoft products. Find how-to articles, videos, and training for Microsoft Copilot, Microsoft 365, Windows 11, Surface, and more.

A popular tactic of criminals is the "fake order" scam. The way it works is that you get a message, usually in email or text, that appears to be a routine confirmation for an order. Of course, you never ordered whatever product or service it's confirming. The message looks common enough, and it says that money will be charged to your credit card or withdrawn from your bank account for the ...

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

Block senders from sending you email in new Outlook for Windows If you're receiving unwanted email, you can block the email addresses and domains you don't want to receive messages from in new Outlook. Add any email address or domain to your blocked senders list to move these messages directly to your Junk Email folder.

What is Secure Boot? Secure Boot is a security feature in Unified Extensible Firmware Interface (UEFI) based firmware that helps ensure that only trusted software runs during a device's boot (start) sequence. It works by verifying the digital signature of pre-boot software against a set of trusted digital certificates (also known as certificate authority or CA) stored in the device's firmware ...

This security update includes fixes and quality improvements that are part of the following updates: January 13, 2026—KB5073724 (OS Builds 19045.6807 and 19044.6807) January 17, 2026—KB5077796 (OS Builds 19045.6811 and 19044.6811) Out-of-band January 24, 2026—KB5078129 (OS Builds 19045.6812 and 19044.6812) Out-of-band The following is a summary of the issues that this update addresses ...

How to add a signature to your Word documents. You can also use the Signature Line command in Word to insert a line to show where to sign a document.