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 It issues digital certificates, signs certificates to verify their validity and tracks which certificates have been revoked or have expired.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

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

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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 use mobile operator billing as a payment option to buy Xbox subscriptions, games, and other content.

Learn how to manage your Microsoft 365 subscription and billing if you purchased it through a third-party retailer.

To learn about digital signatures (also known as digital ID), what they can be used for, and how to use them in Word, Excel, and PowerPoint, see All about digital signatures. Create a signature line in Word or Excel (desktop) In the document or worksheet, place your pointer where you want to create a signature line. On the Insert tab, select Add a Signature Line in the Text group. In the ...