If your recipient is listed on an LDAP directory service, such as the global address list (GAL) used by Microsoft Exchange Server, the recipient's certificate is published to the directory service and available to you together with other contact information. For information about how to add your contacts' certificates to Outlook, see Import, export, or remove a certificate for a contact. You must also have a copy of each recipient's certificate saved with the contacts' entries in Outlook. For information about how to request a digital certificate from a certification authority, see Mac Help. Send an encrypted message Encrypting with S/MIMEīefore you start this procedure, you must first have added a certificate to the keychain on your computer. Microsoft 365 Message Encryption (Information Rights Management) - To use Microsoft 365 Message Encryption, the sender must have Microsoft 365 Message Encryption, which is included in the Office 365 Enterprise E3 license. S/MIME encryption - To use S/MIME encryption, the sender and recipient must have a mail application that supports the S/MIME standard. To use digital signatures, both the send and recipient must have a mail application that supports the S/MIME standard. Any recipient without the corresponding private key, however, sees indecipherable text.Ī digital signature on an e-mail message helps the recipient verify that you are the authentic sender and not an impostor. Only the recipient who has the private key that matches the public key used to encrypt the message can decipher the message for reading. Encrypting an email message in Outlook means it's converted from readable plain text into scrambled cipher text. When you need to protect the privacy of an email message, encrypt it.

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