We have an iPhone app that reads all the contacts of the native address book and may modify some off them. The iPhone address book usually synchronizes with some Google account or some Exchange server.

We noticed that in a few cases (really few) the contacts in Exchange server are duplicated after syncing with the iPhone. Let me list down the facts:


  • User’s Outlook contacts stored on Exchange 2010
  • User’s iPhone (iOS8.1.3) synced with Exchange
  • Our application synced with iPhone


  • Contacts in outlook got duplicated after user used our app (which updates iPhone’s native contacts with extra data)
  • Contacts in iPhone remain OK (i.e. Outlook now has double the amount of contacts that iPhone has)
  • We have seen this happen for two users (out of hundreds)

Known issue:


  • It is clear that this issue has not been resolved. Last update to KB 2711181 was in 2012 – any update since then?
  • We would like to know what triggers this issue (I note https://support.microsoft.com/en-us/kb/2711053 regarding high CPU usage when syncing with Exchange which may be related) so that we avoid triggering the issue

Hope this makes sense – do let me know if you need any more info.


I had a similar issue, the problem was when I imported the contact CSV file into Outlook.

Correct steps:

File -> Open -> import -> Import form Another program file -> Comma Separated Values (Windows) -> Do not import duplicated items. After that, just select next option.

Finally in Iphone accounts settings turn off and turn on again the contacts options.

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