• Per default all outgoing e-mails will be digitally signed.

• Signed e-mails will be sent in clear text.

Click on the signature icon.

Note: a digital signature is not the footer Outlook allows you to append at the end of each e-mail (e.g. Name, Department, Address, Phone, etc).

A digitally signed e-mail (and the corresponding digital signature) is based on cryptographic algorithms and allows the recipient of your e-mail to: 

• verify your identity (because of your DFN-PKI user certificate)
• be sure the e-mail wasn't changed on the way.

• "gültig" is valid and means that the hash value of the electronic signature was computed correctly (this is crypto jargon and basically means the e-mail wasn't changed on the way).

• "vertrauenswürdig" is trustworthy and means that the public RSA key of the sender was included in a user certificate issued by a certificate authority whose certificate chain is anchored in a root certificate included in Outlook's certificate store (even more crypto jargon, but it doesn't prove the sender's identity, you need to look into the certificate itself to see that).

If you click on "Details" you get to see more crypto stuff, e.g. message hash value.

We choose to stay under "Allgemein" and have a closer look at the sender's user certificate.

This is the certificate chain:

• T-TeleSec is the root certificate (preinstalled in Outlook)

• DFN-Verein are the two intermediates

• the sender's user certificate is at the bottom of the chain

• "Erika Mustermann" is the Common Name in the user certificate, this is the proof of identity part.