# Trust S/MIME Signing Certificates in Outlook

By default Hermes SEG uses self-signed S/MIME certificates for encryption and signing. E-mail clients such as Outlook do not trust those self-signed certificates. In Outlook, emails signed with the self-signed certificates show an invalid digital signature error (**Figure 1**).

**Figure 1**

[![image.png](https://docs.deeztek.com/uploads/images/gallery/2023-03/scaled-1680-/odTimage.png)](https://docs.deeztek.com/uploads/images/gallery/2023-03/odTimage.png)

In order to have Outlook trust the certificates, click on the yellow triangle to the right of the e-mail in question (**Figure 2**).

**Figure 2**

[![image.png](https://docs.deeztek.com/uploads/images/gallery/2023-03/scaled-1680-/GIIimage.png)](https://docs.deeztek.com/uploads/images/gallery/2023-03/GIIimage.png)

In the resultant **Digital Signature** pop-up window, click on the **Details** button (**Figure 3**).

**Figure 3**

[![image.png](https://docs.deeztek.com/uploads/images/gallery/2023-03/scaled-1680-/dxXimage.png)](https://docs.deeztek.com/uploads/images/gallery/2023-03/dxXimage.png)

In the resultant **Message Security Properties** pop-up window, click on the Signer e-mail address and then click on the **Edit Trust** button (**Figure 4**).

**Figure 4**

[![image.png](https://docs.deeztek.com/uploads/images/gallery/2023-03/scaled-1680-/ISKimage.png)](https://docs.deeztek.com/uploads/images/gallery/2023-03/ISKimage.png)

In the **View Certificate** pop-up window, in the **Trust** tab, under the **Edit Trust** section, select **Explicitly Trust this Certificate** and click **OK** (**Figure 5**).

**Figure 5**

[![image.png](https://docs.deeztek.com/uploads/images/gallery/2023-03/scaled-1680-/QNmimage.png)](https://docs.deeztek.com/uploads/images/gallery/2023-03/QNmimage.png)

Close and re-open the e-mail in question and the yellow triangle is now replaced with a red ribbon indicating that the **Digital Signature** is trusted (**Figure 6**).

**Figure 6**

[![image.png](https://docs.deeztek.com/uploads/images/gallery/2023-03/scaled-1680-/h4Ximage.png)](https://docs.deeztek.com/uploads/images/gallery/2023-03/h4Ximage.png)