Hi stephenn21,
Welcome to Apple Support Communities. We understand that you're having an issue with your Smart Mailbox refreshing. We'd like to help.
Have you done a restart yet? While it's a simple step, it can help with an issue like this so it's always good to start there: Shut down or restart your Mac - Apple Support
Shut down your Mac
* On your Mac, choose Apple menu
> Shut Down.
* If you don’t want app windows that are open to reopen when your Mac restarts, deselect “Reopen windows when logging back in.”
* A Mac is completely shut down when the screen is black. Some computers also don’t show an active power light or have any fan or drive noise.
* Important: If you’re using a Mac laptop, wait for it to shut down completely before closing the display. If you close the display while the Mac is shutting down, it may not shut down properly and may start up more slowly the next time you turn it on.
Always shut down your Mac before opening the case to install additional memory or other devices inside the computer. You may also need to shut down before connecting or unplugging certain peripheral devices. If you’re unsure, refer to the documentation that came with the device.
You don’t need to shut down your Mac when connecting or disconnecting cables, such as USB-C, Thunderbolt, or Ethernet.
Important: You can force a shutdown if necessary—for example, if your Mac becomes unresponsive—by pressing and holding the power button until your Mac shuts down. You may lose unsaved changes in open documents.
Once powered off, please turn it back on.
Then, if the issue persists, run your Mac in safe mode to see if it can correct the error that is happening. The steps for that can be found here: How to use safe mode on your Mac - Apple Support
Hope that helps.
Cheers!