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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?


  • Mac OS X
  • Apple Mail


  • 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".


Documentation and information provided by the MIT Community

Last Modified:

June 03, 2012

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