Click the three green icons under the email subject, you can see the meaning of the three icons. The green lock means content of the email is encrypted, the green tick icon shows that the email is signed by the sender and the T icon shows that the email's sending time is added by a timestamp server that is forge-proof, tamper proof and non-repudiation.
Click the other three green icons under the sender's address, you can see more information. The first one is the sender's Identity Certificate. The second one, V3 means that it is a V3 Identity Certificate and the last icon is a link to apply for Identity Validation.