---
type: concept
title: Outlook S/MIME Usage
tags: [outlook, smime, encryption, digital-signature]
related: [outlook-certificate-import, smime, dfn-pki-zertifikate]
created: 2026-06-30
updated: 2026-06-30
sources: ["output/rz_uni_greifswald_de_dienste_allgemein_e_mail_e_mail_sicherheit_cert_outlook.md"]
---

# Outlook S/MIME Usage

Outlook S/MIME usage refers to the operational application of digital certificates to ensure the authenticity and confidentiality of email communication. This process follows the initial [[outlook-certificate-import]].

## Digital Signing (Signieren)
Digital signing makes an email "tamper-proof" (fälschungssicher). 
- **Requirement**: A private key and a [[dfn-pki-zertifikate]] certificate must be imported into Outlook.
- **Operation**: Once configured, users can toggle the **Sign** button when composing a new email.

## Encryption (Verschlüsseln)
Encryption ensures that only the intended recipient can read the email content.
- **Requirement**: The sender must have the recipient's **public key**.
- **Operation**: Users select the **Encrypt** button when composing the email.

## Managing Public Keys
Because encryption depends on the recipient's public key, the following methods are used to acquire them:

### Via Signed Emails
1. Receive a signed email from the recipient.
2. Right-click the sender $\rightarrow$ "Add to Outlook Contacts."
3. **Important**: If the contact already exists, it **must be deleted** before adding the new signed email to ensure the public key is updated to the current version.

### Via DFN Address Book
For participants within the DFN-PKI ecosystem, the [[dfn-adressbuch]] can be added to Outlook, providing a centralized directory of public keys.