macOS Sonoma: Apple Mail says the BusyContacts plug-in is incompatible or not allowed

If you upgraded to macOS Sonoma (or a newer macOS release) and Apple Mail reports that the BusyContacts plug-in is incompatible or can’t be enabled, that’s expected.

BusyContacts no longer uses the legacy Apple Mail plug-in on modern macOS. Instead, BusyContacts uses a MailKit-based Apple Mail extension called BusyContacts Mail Assistant (macOS 12+).

Fix: use the Mail extension

1. In BusyContacts, enable capture in BusyContacts > Settings > Integrations > Mail.
2. In Apple Mail, enable the extension:
   • macOS 13+: Mail > Settings > Extensions
   • macOS 12: Mail > Preferences > Extensions
3. Quit and relaunch Apple Mail, then quit and relaunch BusyContacts.

Full details (and limitations) are here:

• Activity List: Adding Mail

If you need the legacy plug-in

The legacy Apple Mail plug-in was only available in older BusyContacts releases and is no longer supported.

• Activity List: Legacy Apple Mail plug-in (no longer supported)