When I sync my Yahoo! contacts with my iPhone it duplicates them in both Yahoo1 Contacts and iPhone contacts.?

Well, this is a bit of a non-answer so far. I've had the same problem starting a few weeks ago (I reckon around the time the 4.1 update made it to my phone).

Originally, I had only one contact each in iPhone, and Yahoo started to get duplicates (2x for each contact). As of recently I noticed that iPhone has multiple contacts as well.

Since then, I have tried a number of things, most recently:

1. I have exported my contacts from Yahoo to a CSV file. Amazingly this came out with NO duplicates at all

2. I deleted all Yahoo contacts and re-imported with the CSV file... this results in no duplicates in Yahoo.

3. I have used the iPhone's: Settings > General > Reset > Erase all Contents and Settings button

4. I restored my iPhone using a recent backup

5. Before syncing with Yahoo for the first time after all this, I change a setting in iTunes: (my iPhone) > Info > Advanced > Replace information on this iPhone: Contacts

6. Sync my iPhone

I figured this would do it, however I end up with the same issues: duplicate contacts on my iPhone, and after syncing I end up with duplicate (sometimes 3 or 4x) contacts in Yahoo.

Before going drastic I did do the above procedure without steps 3 and 4 (i.e. without the erase and restore), and instead unticked the box in iTunes for syncing contacts... this asked if I wanted to erase the ones in the phone, which it did. Then I did the option back in #5, to try to do a one-way sync with correct Yahoo contacts... this still didn't work, hence the above procedure.

I might try a full erase WITHOUT a restore and see what happens.

I figure that if this is a known issue, Apple's concern might not be heavy as they are trying to market MobileMe which is a paid version of this type of sync... getting the free version to work might be a lower priority.

If I discover anything I'll write back.

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Update #1:

OK, so after the above procedure, and running more than a few sync's (both with and without the option in step 5, above), I now have the following:

Yahoo: all contacts are singular (not duplicated).

iPhone: for some reason all contacts from A-Br have 3 copies (sometimes only 2), however all contacts for the rest of my contact list are singular.

Bizarre. If I find more silly behavior I'll write back.

Iphone Contacts Duplicates