Yes. You might have to get it past System Integrity Protection. Here's how:
Delete the DataVaults Folder
Delete the DataVaults folder without losing any important data, and then Mail will recreate it when you try to enable the Mailhub plug-in, hopefully fixing the problem:
You may want to print these instructions, write them down, or open them on another computer or device so that you have access to them while rebooting your Mac.
Click on the Apple menu and choose Restart…. Hold down the Command and R keys so that your Mac will reboot in Recovery Mode. This will enable you to temporarily turn off System Integrity Protection (as instructed below) so that you have access to delete the protected DataVaults folder.
From the Utilities menu, choose Terminal.
Type csrutil disable and press Return. (This is what turns off SIP.)
Click on the Apple menu and choose Restart.
Drag the folder:
to the trash. (See How can I open the Library folder? if you have trouble finding it.)
Launch Mail and click on Manage Plug-ins… to enable the Mailhub plug-in.
You can then repeat Steps 2–5, typing csrutil enable instead, in order to turn SIP back on.