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 

 

 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 

 

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

 Figure 3 

 

 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 

 

 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 

 

 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