I had a request come in to take a look at a users Outlook that had over 500,000 duplicate contacts. He has about 500 unique contacts, but for some reason, they duplicated. When I launched Outlook it initially froze Outlook so I went into Resource Monitor to watch what was going on with the CPU, Disk, Network, Memory, and Outlook was hitting it hard.
After I let Outlook sit and sync for a while (20 minutes) it finally started responding again and I was able to get into the Contacts area. I found an article which Microsoft published that is supposed to help resolve the issue of duplicate contacts. After reading this over, I still involved us doing the work of removing the duplicates, which isn’t very efficient of our time. Also in the article there was a section on importing contacts and telling it “Do Not Import Duplicate contacts” so I was thinking, why can’t I export all of the contacts into a PST file, then delete all the contacts in Outlook, and import them back in from the PST file telling it not to import the duplicates. Even if it doesn’t get rid of all the duplicates, it should do about 90% of the work and leave us a little cleanup to take care of.
I was on the phone with the HelpDesk tech working on the issue, and told him the route I would take with the issue. After some discussion we agree’d that this would be the best method that used the least amount of our time and would be a good first step. If there are no more updates to this, then consider it resolved. If anything changes or doesn’t work, I will update this.