"Signed Email" is like ordinary emails we send everyday but with sender's digital signature attached to it. It can provide assurance of sender's identity and is analogous to a letter with a hand-written signature on it but in a digital format.
Q2. Do I need to put my digital signature (to sign) on every email?
No. There is no need sign every outgoing message. However, you may like to send a signed email if you would like to assure your recipients that an email message really came from you. For example,
- Sending announcement to all staff or students.
- Sending important message to a large group of users via mailing lists, etc.
- Personal email communication
Email virus nowadays like "SoBig" will send out email using spoofed identity. With the use of "Signed Email", recipients can then have an easy way to confirm the sender's identity in email.