Another duplicate question.

Yes, creating a copy for email will work.  But there is absolutely no need to do that. 

The catalog does not create and store copies of your photo files.  It merely creates a list of where they are stored.   It is therefore essential that you let Elements know what you are doing with your files.  Copying, moving or deleting a file using Windows File Explorer does not provide any information to Elements.  For this reason, and I cannot stress this enough, all file operations (copy, move, rename or delete) must take place within the Organizer.  Your failure to do this has resulted in the missing files in your catalog.

When you send a photo via email whether via Elements or via Outlook or other email program, a copy of the photo will be created and embedded within the email.  Nothing happens to the file stored on your computer which is listed in your catalog.  Therefore everything remains the same.  Of course, your email program will store a copy of the photo within the saved email.  If you delete the email, the copy of the photo will also be deleted.  But the original will remain.  If you want to keep track of photos that you have emailed or posted on Facebook, you can put them in an Album or even apply a Posted in Facebook tag to them.  This will not create any duplicate photo files but the information will be stored in your catalog ready to retrieve whenever you want.

At this point, I have lost track of exactly what your question is.  Your question is about duplicates, but are they really bothering you?  And if so, how?  How many total photos do you have in your catalog and what percentage are duplicates?  How much work have you performed already on the catalog, e.g. tagging all of the files and/or applying names via face recognition?  Have you created any Albums or is it your goal to do so in the future?  Have you edited any of the photos and placed them in version sets? 

Since your original question is about duplicate photos, I suppose you might be interested in deleting all of the duplicates.  But if you do so, I would suggest not deleting them from your computer.  Alternatively, simply stack the duplicates so you only see one image in the Organizer's grid. 

@jmillsp said:

I think they go to the Picture folder on the D. drive?

You have told us that you have some files with many duplicates in the Organizer.  If they all have identical names and identical dates and times, they cannot possibly be stored in the same folders on your computer.  I have told you how to find the exact location on your computer.  So my question is for you to look at one of the files that has many duplicates and tell us the exact folder location of each of the duplicates.  That may at least give us a clue as to why you have any duplicates.

Yes, you should definitely copy the files on import from the memory card.

But how are the duplicate files organized?  You can't have the same file with the same name in the same folder.  So where do the duplicate files end up?

So the .json files are text files that contain all face recognition information and possibly other database information.  If you were to delete them, you would lose all face recognition information.

A stack is a tool that is available in the Organizer grid to manage your photos.  In the following screenshot, you will see one of my photos at the top with an arrow at the side.  When I click the arrow, the stack expands to display 3 photos in the stack.  One of the photos is a raw file which I automatically stack with the identical jpeg image.  The third file with the edited suffix in the name is an edited file, saved as a jpeg copy.  Again, I automatically stack edited files with the original in what is known as a version set.  The edited file sits on top of the stack.  And the stack or version set can be collapsed to display only a single thumbnail by clicking on the side arrow.

If you select any photo and right-click on it, you will have a choice to Go To Folder.  Click that option and the folder in which the file is stored will be selected in the Folders panel on the left.  (Make sure you are in View as Tree rather than View as List.)

Do this with each of the duplicate files and this will give us an idea of where the files are actually stored on your computer.  Alternatively, the location of the file may be found in the Info. Panel on the right of the screen.  It is listed under Location.  Usually, the full path cannot be seen.  So you can click on the Location which is a link that will take you to a Windows File Explorer window containing the file in question.

One other thing you should do is to select All Missing Files from the Find menu.  You mention having the question mark icon in your original post.  Finding all missing files will let you see whether you still have any in your catalog and if you do, you can clean up the catalog by selecting all the found missing files and deleting them.

. . .  and a couple more questions:

Have you created a backup of your photo files and possibly imported the backup files into your catalog?  The backup files will generally have a name starting with B00.  Where have you stored your backups?

What version of Elements are you using?

When you say you are finding some photos with multiple duplicates, we need to have more information about those duplicates. 

Are the duplicates in stacks or version sets? Have they been edited by you?

Do the files have exactly the same names?

Do they have exactly the same date and times?

How many physical drives do you have attached to your computer and how many drive partitions (drive letters) do you have?

Where are the files stored on your computer?  Give us the exact path of some duplicates and state whether they are stored on an external or internal drive.

How do you import files to your computer?

Have you cloned any drives where your photos are stored, either to add a new drive to your computer, to move a drive to a new computer or to replace a drive on your computer?