I had the same problem. Here is my solution, with required resolving three problems with Outlook’s data files:
- Outlook was using the wrong PST files
- The PST file was far too large, and
- The PST file was corrupted.
In my case, all three were related: 2 and 3 meant that I had to create a brand new PST file.
After I completed all three steps, my iPhone sync’ed like a charm – and in a lot less time than previously.
Background
Apple’s support article on Sync issues (https://support.apple.com/en-us/HT203300)lists a number of steps. However, it does not address Outlook’s data files (PST and OST), which were the root of my problem. Accordingly, there is very little in this post about the iPhone and iTunes.
I was connecting Outlook 2010 to my phone with iTunes and a USB cable, but I assume that the steps below would apply to syncing and of the Outlook desktop versions (eg. 2007, 2010, and 2013) via iCloud, or iTunes via WiFi.
Note that iTunes only syncs Calendar items and Contacts. ITunes does not support/ sync Outlook’s Tasks or Categories. To sync those, you’ll need a third-party app.
Outlook’s Data Files
Outlook has two types of data files: OST and PST. For more information, see
https://support.office.com/en-us/article/Introduction-to-Outlook-Data-Files-pst- and-ost-6d4197ec-1304-4b81-a17d-66d4eef30b78
and
https://support.microsoft.com/en-ca/kb/287070.
You can access the default files in two ways:
In Outlook 2010, click the File tab, Account Settings, and then click Account Settings.
On your PC, go to Control Panel > Mail 32-Bit > Data Files
Other Information
General warning:
Back everything up before you do anything: Close Outlook, find the PST files, and put copies in the subdirectory.
Naming conventions:
Outlook 2010
The desktop application. Not to be confused with its rebrand as “Outlook.com”, (aka Outlook Web App or OWA) and the desktop app.
Hotmail
That’s what I still call it, and I wanted to avoid confusion between Outlook.com as noted above.
Outlook.PST
The data file that Outlook 2010 creates for itself (as opposed to Hotmail.OST or Gmail.PST for the data files that support any linked email accounts.)
Resolving Problems with Outlook’s Data files
1. Confirming the default data file and email account
Short version:
The forced upgrade in October 2016 from Hotmail Connector to MS Exchange changed the default from my desktop data file to the Hotmail data file. (See https://www.howto-outlook.com/howto/outlookcommigrationinfo.htm) for more information.)
Since I had not used Hotmail’s Calendar, it was empty, and when I connected my iPhone, the existing entries (from Outlook 2010) were wiped. The first part of the fix is therefore “check that the default Data file is Outlook.PST, not the Hotmail.OST account”. You’ll get a warning message as set out here.
More information:
Outlook 2010 requires that you set the default email account (the first tab) and then the default data file (the second tab). I had a Hotmail and a Gmail account and was running Outlook 2010’s default Calendar and Contacts. As a result, the Email tab listed the two email accounts; the Data Files tab listed the files for the email accounts plus the Outlook data file.
All the data files are configured to accommodate all of Outlook’s 2010 functionality. In my example
if you have set up Outlook to connect to a Gmail and a Hotmail (Outlook.com) account, then you’ll have one data file for each. These data files are store the Hotmail Calendar and Contacts that you can see on Outlook 2010.
The first part of the fix is therefore “check that the default Data file is Outlook.PST (or wherever you store your Outlook 2010 data), not the Hotmail.OST account”. (Microsoft didn’t notify me either that they were discontinuing Hotmail Connector, or that the default Data file would change.)
2. PST file is too large
iTunes will have problems syncing if the Outlook.PST file is too large.
One site suggests that the limit is 2GB for some PST formats, and up to 50GB in others. My take is that if any of your PST or OST files are that large, then you have a data management problem, eg. you’re using email to share files instead of collaboration (SharePoint) or data storage tool (Box, Dropbox, etc.)
My Outlook.PST was nearly 3GB. After the changes below, it is now a respectable 150K, with fifteen years of appointments and 4400 Contacts (many with profile photos).
Your first action should be to reduce the PST file size by following the instructions here: https://support.office.com/en-us/article/Reduce-the-size-of-Outlook-Data-Files-p st-and-ost-e4c6a4f1-d39c-47dc-a4fa-abe96dc8c7ef
An additional tactic not on that list: ensure that copies of emails are NOT kept in the Outlook 2010 file. (I had somehow set this up when linking my Gmail account, which is why the PST file got so large. In my case, clicking “Mail” under the Home tab showed three folders - Outlook, Gmail, and Hotmail – and the Outlook folder’s Inbox and Sent messages had copies of all the Gmail emails.
To change this: open the Email tab as noted above, select Change, then More Settings. You should not need to click “Save a copy of the sent mail on the server”, because you’re already saving it in your main PST file. Send a few test messages to yourself to be sure.
If you are worried about accidentally deleting the emails permanently, don’t delete them, but instead see the “Creating a New Data File” instructions, below.
3. PST file is corrupt
ScanPST.exe
Outlook comes with ScanPST.exe, a tool to repair PST files: https://www.howto-outlook.com/faq/usingscanpst.htm. It doesn’t clean everything on the first pass; run it repeatedly until it no longer returns errors, and then run the Compacting tool in the “reduce PST size” link above.
Exporting/ Reimporting Data
You can also try to export the PST file piecemeal - one file for Contacts, Calendar, Tasks, etc. – (https://support.office.com/en-us/article/Export-or-backup-email-contacts-and-cal endar-to-an-Outlook-pst-file-14252b52-3075-4e9b-be4e-ff9ef1068f91), and then create a new PST file (https://support.office.com/en-us/article/Create-an-Outlook-Data-File-pst-to-save -your-information-17a13ca2-df52-48e8-b933-4c84c2aabe7c) and re-import the pieces.
You can also export to Excel, CSV, or to Access; this loses some functionality (eg. profile photos on Contacts), but exporting to a different format may clean out the source of the file corruption.
Once you’re satisfied that you’ve copied all the information from the old (corrupted) file to the new one, delete the old one.
Copy and Paste the Data into a new PST file
A third option: create a new PST file in a new folder (https://support.office.com/en-us/article/Create-an-Outlook-Data-File-pst-to-save -your-information-17a13ca2-df52-48e8-b933-4c84c2aabe7c), and then copy and paste the entries from the old file to the new one (https://support.microsoft.com/en-ca/kb/197038). Again, once you’re satisfied that you’ve copied all the information from the old (corrupted) file to the new one, delete the old one.
FIN
