Q: Why do I see someone else's certificate in my Keychain?
- See other people's certificates listed when view Certificates in the Keychain utility. Why?
- The mostly likely cause of this is that someone sent you e-mail which they digitally signed with their MIT certificate.
- These emails will come in with a yellow bar across the top that says, "Unable to verify message signature".
- Apple Mail automatically adds such certificates to the Keychain, it's possible that other email clients do that too.
- It does not grant them any access to your computer, it simply remembers that those digital signatures are valid for future e-mails.
- You may delete these certificates, or trust the sending person, and then all messages from that user will be "Trusted".