About digital signatures and certificates in Office, and buying a digital certificate from a certificate authority or create your own.

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 It issues digital certificates, signs certificates to verify their validity and tracks which certificates have been revoked or have expired.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

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摘要 Email签名在业务通信中创造专业一致性，并确保收件人在每封邮件中都有你的联系信息。 在Outlook 中，可以设置多个签名， (内部与外部、个人与业务) 的不同用途，并选择是自动将其包含在新的电子邮件、答复还是转发中。 签名可以包括文本、链接、图片和图像 (，例如手写签名或徽标 ...

Download Microsoft Authenticator Microsoft Authenticator is a mobile app that helps you sign in to all your accounts without using a password.

This page features a list of common error codes and solutions. Learn how to find your error code quickly.

Troubleshoot problems with Microsoft Authenticator You can resolve problems with Microsoft Authenticator by checking the tips in this article and reviewing some of the known errors.

Learn how to set up your user account for multifactor authentication with Microsoft 365.

Learn how to install the Microsoft 365 Copilot mobile app on your iPhone or iPad and use the apps with Microsoft 365.