Before performing the following steps, first make a backup of your database by going to File and clicking Backup. This is just a good idea before doing anything that is going to make a large change to the database.
The easiest fix is to first figure out which day the duplication occurred. You can do this by scrolling through contacts and seeing at the bottom-left of the screen where it shows the date created. Find the common date for the records, which should be the more recent of the two copies of the contacts. (if the date is identical for all of the records, ignore the rest of this email and give us a call at 281-299-3161 x2, as that makes it a bit more tricky to clean up, and generally, we'll need to take a look with you on a remote desktop session to figure out the best way to move forward)
Once you know the exact date this occurred on, you can perform a query to find only those records, and delete them. To do so, above the contact phone numbers is a drop-down menu labelled Query. Drop that down and select Query.
For the field selection, choose Date Created. Leave the Operator on Is.
Next, select the date the duplication occurred and then click OK.
The number of records at the top-left should have cut by about half.
Next, you'll need to delete these records. To do so, click F5 on your keyboard, which should switch to a list view. Click on any record in the list, and click Control + A on your keyboard to select all records. Finally, hit Delete to begin deleting these duplicated records.
After the contacts are deleted, you'll get a pop-up asking about deleting companies. These company records should also be deleted, as they are now orphaned, and no longer have a contact that is tied to them (and they we're duplicated as well as the contacts from the sync, so this will also clean up that table).
Once the deletions have finished, hit the Sync button and click OK to re-sync with Outlook, which will delete the records that were just deleted from your CRM, leaving you with one copy of each contact in your CRM and in Outlook.