To send digitally signed mails, you need

• your personal certificate and the corresponding password (instructions here)
• installed Office 365 with Outlook with your Uni Bayreuth mail account set up (instructions here)

Open Outlook and click File up left and then Options in the left area.

In the newly opened window, click Trust Center on the left and then Trust Center Settings... to the right.

Another new windows opens. In it, click Email Security on the left side and then under Digital IDs (Certificates) onto Import/Export...

Again, a new window will appear. Next to Import File:, click on Browse... and select your personal certificate file.
Afterwards, enter the password for your certificate file. You have defined it during the download of your certificate – it is independent from your Uni Bayreuth user account password!

Once you're done, click OK.

Confirm the security prompt asking if you want to import the private key from your certificate file with OK.

Your certificate has now been imported.

Back in the Trust Center, please tick the check boxes as shown in the screenshot, so only tick

• Add digital signature to outgoing messages
• Send clear text signed message when sending signed messages

After that, next to Default Setting:, click on Settings...

The window Change Security Settings opens.

Tick the checkboxes as shown in the screenshot at

• Default Security Setting for this cryptographic message format
• Default Security Setting for all cryptographic messages
• Send these certificates with signed messages

and select under

• Hash Algorithm: SHA256

and under

• Encryption Algorithm: AES (256-bit)

Save by clicking OK.

You can now close the Trust Center by clicking OK.

From now on, your mails will be sent digitally signed. This can be checked by verifying that Options -> Sign is selected when composing a new mail.