Outlook S/MIME certificate expiration

Question

I am using a certificate in Outlook to encrypt and sign messages. Everything work great. My certificate is going to expire next year. The following is unclear to me:

1. Should I get a new certificate, or is there a way to renew my current certificate?

2. When I have the new/renewed certificate, do I have to tell all the people I'm communicating with that I have a new/renewed certificate?

3. What will happen if someone sends me an E-Mail, using my old public key, and I have the new/renewd certificate installed in Outlook.

Answer 1

1. You can either issue a new certificate or renew your existing certificate (ask you certificate issuer). No difference here, each individial message is encrypted/signed with a particular certificate of choice.

2. No, you don't need to. This is because you sign your messages with private key and message can be validated with your public key (included in the message). But if you're using non-public (LDAP) address book, you may need to update your public key (certificate) for senders who need to send you encrypted messages.

3. They can't encrypt the message with the expired certificate (public key).