Hey @Axcess02! Thanks for posting about this here.
The 6-digit code that you mention is generally sent if you try to log in to your own Dropbox account from a new device/browser, and you shouldn't receive it when they try to access the files you've shared with them or be sent to your email address, for that matter.
Are you following these steps to share files with these users?
Do they have Dropbox accounts of their own to access your files? When being asked to log in, they should insert the credentials (email address + password) of their own Dropbox accounts, and not yours.
Let me know when you've got updates!