Technical Tip

Contact Sync Optimization – Eliminating Outlook Performance Issues

Last Updated: January 2026

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Overview

Recent Microsoft Outlook and Microsoft 365 changes have introduced background contact updates that can significantly slow contact synchronization. These updates are primarily caused by the Outlook Social Connector (OSC), which may modify contacts even when no meaningful changes have occurred. This behavior leads to unnecessary item updates, extended synchronization times, and increased battery usage on mobile devices.

This document explains the cause of the issue, its impact on contact synchronization, and the recommended configuration changes required to optimize performance.

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Root Cause: Outlook Social Connector

Microsoft has been testing and deploying new background contact update mechanisms associated with the Outlook Social Connector. These updates can affect contacts in any mailbox, including shared and resource mailboxes, and may occur even when the contact data has not changed.

Although service accounts are not intended to be affected, real-world environments have shown that service and sync source mailboxes can experience these unnecessary updates.

Public Folder contact sources currently appear to be exempt from this behavior.

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Impact on Contact Synchronization

When the Outlook Social Connector is enabled, Outlook may update contact information using data from the Global Address List and other social data sources. Each update causes the contact item to change, which triggers synchronization logic to reprocess the item.

This results in a repeated update cycle often referred to as a “ping-pong” effect. The outcome is excessive processing, long synchronization times, and unnecessary workload on both servers and clients.

In many environments, synchronization that should complete in under a minute can take an hour or longer when the Outlook Social Connector is enabled.

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Required Configuration: Disable Outlook Social Connector

To optimize contact synchronization, the Outlook Social Connector must be disabled through policy-based configuration. Disabling the add-in locally is not sufficient.

In Office 365 or Hybrid environments, both cloud-based policies and any existing local Group Policy configurations must be implemented.

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Microsoft 365 / Office 365 Configuration

This is the recommended and preferred approach for modern Microsoft 365 environments.

Sign in as a Global Administrator or Tenant Administrator.
Navigate to the Microsoft 365 Apps Admin Center at: https://config.office.com/officeSettings/officePolicies
Create a new policy named “Disable OSC”.

Apply the policy to all users or to a dedicated security group containing at minimum:

Source mailboxes used for synchronization
Any users who open or access those source mailboxes
When configuring policy settings, search for “Social”.
Enable the setting “Turn off Outlook Social Connector”.
Save and activate the policy.

Most organizations choose to apply this policy to all users, as the Outlook Social Connector typically provides minimal benefit and frequently introduces performance issues.

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DidItBetter Software Configuration Note

If the Outlook Social Connector cannot be disabled for all users, contact your DidItBetter Software representative to enable the “Ignore Destination Item Changes” option within the synchronization template relationships.

If this document was provided by a DidItBetter Support Engineer and access to the replication server exists, this option may already be enabled.

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On-Premises Active Directory Group Policy

For on-premises or hybrid Exchange environments, the Outlook Social Connector should also be disabled using Active Directory Group Policy.
Create the Group Policy "the Microsoft way" for most all configurations. 
Microsoft - Manage the Outlook Social Connector with Group Policy

Microsoft-provided ADM or ADMX templates should be used and applied according to Microsoft best practices. The policy must be applied to:

Mailboxes acting as synchronization sources
Users who access or open those mailboxes

If a local Group Policy exists and the organization uses Office 365 or a Hybrid configuration, both the local and cloud-based policies must be implemented to ensure consistent behavior.

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Additional Microsoft Reference

Microsoft documentation on cloud-based policy management for Office applications can be found at:
https://techcommunity.microsoft.com/t5/office-365-blog/the-new-cloud-based-policy-management-service-for-office-365/ba-p/480676

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Completion Checklist

Outlook Social Connector disabled via Microsoft 365 policy
Outlook Social Connector disabled via local Group Policy if applicable
Policies applied to all synchronization source mailboxes
Synchronization performance verified after policy application

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Other Tips on settings for other issues:  Not seeing the folders created, Icloud, Calendar event settings on mobiles  

IPhone Settings for Contacts, Calendars, Email and Reminders:
If Calendar items are missing on the phone but are in your Outlook, set to sync all calendar appointments. There are similar settings for Androids located HERE

We suggest turning off iCloud on iPhone (and in Outlook) for Calendar, Contact, Mail and Reminders sync to iCloud. Syncing to this site could be considered a security breach for your organization and can allow iCloud to change the data inappropriately as some of their IOS updates have in the past. 
TIP: When prompted from the phone, select Remove Icloud data from the phone.  

See link for Duplicate Contacts appearing on iphone: Duplicate Outlook contacts appear in iOS Contacts app - Exchange | Microsoft Learn

For those with a BYOD policy (Bring your own device to work) users can use office365 services on their devices and in order to do this in a secure way, we suggest a conditional access policy that “Requires app protection policy” as per this link:
https://learn.microsoft.com/en-us/entra/identity/conditional-access/concept-conditional-access-grant#require-app-protection-policy

 

 

Items not showing up on your phone? 

Not seeing Calendars or Contacts on Iphone but they are in outlook?

First, make sure you have created an account for work Email on your phone.

Then on the phone in the Account Settings for that Exchange Mail account, select to show and sync contact and calendars, Reminders and Notes

On the phone, do this in the Account settings for your work email profile

In the picture below, the account is called Exchange  - with account settings shown.
Activate the options for all.

Note: mail days to sync is not relevant here, but can be set to your preference.
 

Microsoft 365 (Outlook for iOS) - View multiple calendars at the same time

Sync all events and for the default exchange calendar, the "Work Calendar".
Then, on the phone, go to the Calendars app, and select Groups - and select all Calendars desired to be shown on your phone.
If you are syncing to the default Calendar, unless it has been turned off, turning it on isn’t necessary.  If you are syncing to non default folders, you may have to select them.

IF syncing Contacts with missing Contacts on the phone, be sure to go to the Contacts app and Groups and then select the appropriate folders to sync.

 

 

Other Tips on Calendars:

Calendar appointment invites must be accepted for Add2Exchange to sync the appointment.

Add2Exchange/Add2Outlook will NOT copy a synced copy of an appointment; it must be original and not dragged from someone's Calendar.

If the text "Copy:" is in the front of the subject of the item, this is an automatic function of Outlook when you copy an item to a calendar. Avoid manually copying item as they may be a copy already and then they will not sync.  Make the item in the source folder manually and it will sync.

 Be sure to have a direct relationship created from the source folder (i.e. the folder the new appointment was made in) to each destination folder (target folder, i.e. the folder(s) you want the new appointment to sync to). This also applies to Contact sync items.

 

 Recurring appointments should have an end date for Calendar Appointments. 

Tip: How to Control Outlook recurrence patterns using group policy: https://support.microsoft.com/en-us/kb/2548319
 

The sync speed is also affected by the recurring appointments with no end dates. Those with no end dates take longer.  You can use the Add2Outlook Toolkit to fix those no end date appointments and set the recurring end date to 5 or 10 years in the future automatically.  Changing the end date from within Outlook will lose any one off instances.   A recurring appointment with no end date actually ends in 4500 AD, or 2500 years from now.  Those types of recurring appointments add up quickly and take much time to process.  A daily recurring with no end date equates to 925000 appointments.  Use the Toolkit to resolve this.

Calendar Tip:  Consider archiving your SOURCE AND DESTINATION Calendars so there isn't as much to consider during replication.   Also, older versions of Outlook used to create the appointments don't conform to the same object model.  Moving old items which are not considered in syncing will maintain data integrity and speed up syncing and user searches.  Use the internal Archiving facility of Outlook or ask your Diditbetter Support Representative to use the Add2Outlook Toolkit to archive easily.  The Toolkit makes a subfolder under the existing Calendar with the name "Calendar Archive" and will move Calendar appointments before a certain date you can choose and can be run on users in our distribution list.  You can also use the online archive utility in Outlook and the Add2Outlook Toolkit to keep Calendar items under 20K but certainly less than 50K items.   Archiving can do that easily and speed up syncing.

How to Clean a Mailbox:
Use the Add2Outlook Toolkit - be careful!
http://www.howto-outlook.com/howto/cleanmailbox.htm
https://support.office.com/en-sg/article/Delete-or-archive-older-calendar-items-e57d6c8c-2e65-455a-b99b-623d091358dc

Description of common scenarios in which Calendar information may be removed from the Calendar or may be inaccurate: https://support.microsoft.com/en-us/kb/899704

The following tips taken from the WEB which seem like good practices and have been slightly modified:
Microsoft Outlook is a powerful calendaring and scheduling tool. This document covers best practices, do and don’ts and tips when utilizing Outlook calendar functions to avoid problems and work optimally.

OUTLOOK MEETING REQUESTS: ESSENTIAL DO’S AND DON’TS

1. Make a choice – When a meeting request shows in your Inbox make a choice for each request by selecting either Accept, Tentative or Decline. By making a choice, you keep the meeting organizer apprised of your decision and you prevent the meetings that you want to attend from being accidentally deleted. If you need to attend a meeting but can't at the time it is scheduled, you can propose a new time for the meeting.

Normal default calendar sync relationship settings are that we do not copy tentative meetings.   If you get a copy of a meeting invite from any other user, do not decline it or it can cancel the original meeting from the original recipient.  Never reject someone else's meeting or decline it if it’s not yours.
It is wise never to manually copy an item to another folder, just make it there.
Also if an item is an invite to you, and you accept it, if a relationship is set from your calendar, it will then sync to other users.  If you’re on the invite list and you do not want to accept the meeting you can reject it.

Tips: Again, if you are not on the original invite list as a meeting recipient, and the item has been copied to you through Add2Exchange or Add2Outlook, do not decline the meeting.  If you are syncing from other source calendar folders to yours and if there were four people which were invited to the meeting and you were not, and you have a relationship to your calendar from the other users, then you’ll have four copies from the four people that were invited and accepted the meeting from your organization.  One will be copied (usually with the with the initials for each person) being copied into your calendar from each user.  You should get no invites

Do not to delete a copied meeting request because this is one way that meetings get "lost." or cancelled.

NOTE: When viewing or responding from a smartphone - Some smartphones may experience calendaring issues when accepting invites. To avoid any potential issue, it is recommended that you accept invites from your inbox on your computer.

2. Process meeting requests in order in which they come into the inbox (oldest first). If you do not process meeting requests that are related to the same meeting in the order that they are received, you may not receive any updates to the meeting.

3. Keep meetings from vanishing - If you run Outlook on two computers or a mobile device and accept a meeting while using one of them, don't delete the meeting request from the Inbox on the other computer. If the request is still there, accept it again. Deleting a request on one computer/device after accepting it on another computer/device can cause the meeting to disappear from your calendar.

4. Process meeting requests and updates from the Inbox - Always accept or decline a meeting request from your Inbox. Yes, Outlook allows you to accept or decline a meeting from its time slot on your calendar, but that can leave the meeting request in your Inbox. If you delete the request from your Inbox it could cause the meeting to disappear. Also, leaving the meeting request in your Inbox might confuse you later and definitely leaves any delegates you appointed wondering about whether the meeting was accepted.

Soon after a meeting request arrives in your Inbox, a piece of Outlook code - nicknamed the "sniffer" - automatically adds the meeting to your calendar and marks it as tentative. This is a fail-safe to keep you from missing the meeting in case you don't see the request in your Inbox. However, the sniffer doesn't reply to the meeting organizer. You still need to do that by accepting, accepting as tentative, or declining the request.

NOTE: Mobile Device users: There are some bugs when accepting a meeting from some mobile devices. The meetings are not syncing consistently. It is recommended when possible to respond to meeting invites from your inbox on your computer.

5. Send updates - After modifying one of your own meeting requests, remember to click the Send Update button to send the updated request to all recipients.

• Cancel a single meeting - Need to cancel a meeting? Notify the people you invited by deleting the meeting from your calendar, select Send cancellation and delete meeting, and then send the cancellation to everyone you invited.

• Cancel recurring meeting - If you, as the meeting organizer, are ending a recurring series of meetings, open the meeting on your calendar, set a new end date, and then send an update. This keeps the past meetings on everyone’s calendars, but future occurrences after the end date are removed.

• Change meeting organizers - If a recurring meeting is changing to a new organizer, there is no way to reassign the ownership of the meeting. The original organizer should send an update with a new end date - the past meetings remain on everyone’s calendars, but future occurrences after the end date are removed. The new meeting organizer should send a new meeting invite for meetings in the future.

• Don't move meeting requests - Don't move a meeting request from your Inbox to a different folder before you accept or decline the request or before the meeting appears in your calendar.

BEST PRACTICES – WORKING WITH OUTLOOK CALENDAR

Have all clients work on the same Outlook application version

While it seems that there is not a whole lot of difference sometimes between application versions, it does make a difference in avoiding problems when delegates are on a different application version than the owner or you use two different computers/devices with different versions. It is recommended that owners and delegates be on the same version of the application and if you use more than one computer (work vs. home) or device, be sure that both are using the same application version.

If the recurring appointment was made in a different version of Outlook you will need to recreate the appointment in the current Outlook and specify an end date.  See tip above.

Limit the number of delegates who have access to your calendar

Outlook does not have a defined limit for the number of delegates you can add to your mailbox. Although Outlook does not have a defined limit for delegates, other resource limitations will eventually limit the number of delegates you can add to your mailbox. When you reach this limit, you receive the following error message when trying to add a new delegate:

   Unable to forward meeting-related messages

To prevent incorrect or missing meeting information, it is recommended you use minimal delegates with Editor Permissions if not just one. Decide whether the delegate or the mailbox owner will process all the meeting requests. If more than one user must have access to your mailbox, carefully consider whether these users have to be delegates. You may want to give the user Review permissions to your folder instead. To give user Reviewer permissions, follow these steps:

1. Right-click the Calendar folder and then select Properties.

2. Select the Permissions tab.

3. Select Add.

4. Select the name of the user who you want to give Reviewer permissions to and select Add. Next, select OK.

5. In the Name box, select the user name and then select the appropriate permission level using the dropdown menu in the Permission Level box.

6. Select the Apply button, then OK.

Schedule end dates on recurring meetings

When scheduling recurring meetings, it is highly recommended a definite end date be used. If a meeting recurs weekly or monthly over 6 months or a year, it is recommended to make the recurrence end date at 3 or 6 months. When a definite end date is used you may prevent issues that may occur if you have to update the meeting several times. When a recurring meeting must be modified often, changing the recurrence end date after the fact can cause those “exceptions” or modifications to be lost.

NOTE: Outlook allows a total of 123 revisions to a recurring meeting, so keep recurring meetings limited to 3 – 6 months maximum.

Refresh Data

It is recommended from time to time or when you are seeing discrepancies, to refresh your Outlook windows. Do this by:

1. From the Send/Receive Tab, in the Send & Receive group, select Send Receive All Folders.

2. This will refresh all folders and views for Outlook.

HOW CALENDAR INFORMATION MAY BE REMOVED OR BECOME INACCURATE

There are several known scenarios that may occur in which calendar information may disappear, be removed or be inaccurate when using Outlook or Outlook Web Access. This section describes these scenarios.

Forwarded meetings can lead to inaccurate information in the calendar

I. Forward request as the meeting organizer

The meeting organizer should not forward meeting requests. Consider the following scenario:

1. If as the meeting organizer, you forward a meeting request to a recipient not in the original attendee list.

2. Because the meeting was forwarded and the recipient was not added as an attendee, the recipient does not automatically get added to the attendee list.

3. As meeting organizer, you change the time and send an update to the attendees.

4. The recipient who received the forwarded meeting request does not receive the update.

To include a new meeting attendee in an existing meeting request, the organizer should add the name to the meeting attendee list and send an update to the original meeting.

II. Forward request as a meeting attendee When you forward a meeting (recurring or single-instance) to a new attendee, the new attendee is not added to the original meeting unless the attendee sends a meeting response. All updates to the meeting are not sent to the attendee, resulting in out-of-date information in that attendee's calendar.

Send Update when changing a meeting as the meeting organizer

When meetings you organize are changed, you must click Send Update to make sure the changes are sent to everyone you invited to the meeting.

To send an update, follow these steps:

1. In Outlook, open the meeting you organized.

2. Change the meeting time, date or details.

3. Click Send Update to send an updated meeting request to the invitees notifying them of the changes.

NOTE: 1) After you change a recurring meeting, wait before making other changes to allow for synchronization across all invitees. 2) Outlook allows a total of 123 revisions to a recurring meeting, so keep recurring meetings to 3 – 6 months  - or yearly as a recommended maximum. If a group policy was create for recurring appointments, We suggest the maximum of 10 years, 5 years recommended. 

Mobile Devices - smartphones:

Here are some great links to turn off the contacts sync to iCloud or Google.

Please make sure the People who are in the Add2Exchange/Add2Outlook sync have the Contacts or Calendar turned off on the iPhones.  Refer to tip above.

How to turn off Google Sync on an Android device: http://support.diditbetter.com/turn-off-google-sync.aspx

Turn off items to sync with ICloud: https://support.apple.com/kb/PH2613?locale=en_US