Step 1: Open Outlook and go to Options
After successfully opening your Outlook application, please go to File in your ribbon bar and click in the upcoming menu bar Options.
Step 2: Open the Trust Center
Please call this up via the sidebar Trust Center (in some Outlook versions also called "Security Center"!) and select "Trust Center Settings...",
Step 3: Import your user certificate
You can skip this step if your certificate has already been imported into the Windows certificate store.
Through the button "Email Security", you can import your user certificate by clicking on "Digital IDs (Certificates)".
Now select the certificate file you exported and specify the password of the file.
By selecting the "OK" button you confirm the import.
Step 4: Activate the user certificate
First, activate the selection box "Encrypt message contents and attachments"to ensure that outgoing messages are always cryptographically signed.
To activate your imported user certificate, please click on "Settings".
In the window that opens, please check that your user certificate has been automatically selected as the encryption and signing certificate. If not, you can change that via the "Select ..." button. The remaining settings should be selected as shown. It may be necessary to set the "hash algorithm" on "SHA256" and the "encryption algorithm" on "AES (256-bit)".
After doing this, please confirm with "OK" and close the Trust Center window and Outlook options with"OK" as well.
Step 5: Encryption when composing an e-mail
Microsoft Outlook will now automatically sign your emails digitally. When composing an e-mail, go to menu point "Options" This button leads to possibilities for encrypting the e-mail. Please note, however, that you can only encrypt e-mails if you have already received a signed e-mail from all recipients of the e-mail you want to encrypt.