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Why does S/MIME stop working when BusyContacts Mail Assistant is enabled?

BusyContacts Mail Assistant and Apple Mail's built-in S/MIME encryption cannot currently be used at the same time. When Mail Assistant is enabled, S/MIME signing and encryption are unavailable in Apple Mail.

BusyContacts Mail Assistant uses Apple's MailKit extension system to receive and process messages for the BusyContacts Activity List. S/MIME also uses Mail's message-security system.

MailKit treats an enabled message-security extension as the active handler for message signing and encryption instead of combining it with Mail's built-in S/MIME handling. This separation avoids having two security systems process the same message, but it means BusyContacts Mail Assistant and S/MIME are currently incompatible.

Choose the feature you need:

  • Mail activity in BusyContacts: Enable BusyContacts Mail Assistant. S/MIME will be unavailable.
  • S/MIME in Apple Mail: Disable BusyContacts Mail Assistant. BusyContacts will not capture new Mail activity.

Use S/MIME in Apple Mail​

  1. Open Apple Mail.
  2. Choose Mail > Settings > Extensions.
  3. Disable BusyContacts Mail Assistant.
  4. Quit and reopen Apple Mail.
  5. Try signing or encrypting the message again.

Disabling the extension restores S/MIME. Mail activity that BusyContacts already recorded is not removed.

You can enable BusyContacts Mail Assistant again when you no longer need S/MIME. We have not verified a macOS version where both features work together.

For more information about Mail activity, see Activity List: Adding Mail.

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