I have been using Apple Mail and S/MIME for quite a while now. While I have been starting with a commercial certificate, I now decided to switch to a certificate from a dedicated CA (recognized by all people to whom I correspond).

Both certificates are in my keychain, both have been issued for my email address, are valid and trusted.

Apple mail keeps using the certificate that has been in the keychain first.

Does anybody know a way to make Apple mail using the other cert? I don't want to revoke trust from the first cert as I still need it for decryption.

Thanks in advance!


  • Have you selected the new one in Settings > Accounts > Advanced > S/MIME ? – not2savvy May 29 '18 at 22:04
  • Hmm. Which Settings do you mean? Apple Mail or the OS Settings? In the Mail Settings I cannot find any Advanced Tab. – Norbert May 30 '18 at 6:41
  • Me stupid - I didn't read your question properly and was talking about iOS Mail. I've posted an answer which is hopefully better. – not2savvy May 30 '18 at 8:34

This can be achieved from the Keychain Access application:

  1. Open Keychain Access
  2. Select My certificates or search for your certificates
  3. On the certificate you want to use for your email address, right-click and select New identity preference (or select from File menu)
  4. Enter the email address you want the certificate to be used with

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