Below is some valuable information for speed killers for Contacts Sync:

Update Jan 2024:

Microsoft has been testing new technology which updates contacts unnecessarily as part of social connector and has extended to any contacts in any mailboxes in O365.  This is not supposed to happen, and seems like an oversight in their testing, but it does and creates delays in syncing and kills battery life on mobile devices.  It is important that if you are doing contact sync and the source contacts are in a mailbox or resource, that (at least) the source and any users who have it open should be excluded from the policy, even if you have a local Group Policy in place, you will need to implement both in any O365 or Hybrid environment.  At present it seems Public folder source folders are exempted from this.  Be sure to check that if you have a local Group Policy in AD in effect, verify it is not running an osc_disable.bat file.  This was an older and ineffective way to resolve this.  The ADM files for local AD is the correct way to do on premise exclusions.  If that osc_disable batch file is in place, be sure to remove that policy and implement the "Microsoft Way" for ADM files below for on premise, but if you are in O365 or planning to migrate, we recommend both policies in place.  Be sure to apply this policy to any sync source folder mailboxes or resources and consider applying it to all users.  See Tip below on O365 implementation.

Contacts:

We have found the Microsoft Outlook Social Connector (in Outlook) updates the contacts from the GAL and other social platforms which negatively affects syncing, causing unnecessarily updated items. This causes long sync times.  Access and other options of the Social Connector can be granularly controlled through Active Directory Group Policy rules, but the machines have to be on the domain.  A full or partial turning off of automatically installed Outlook Add in for Contact Sync for your organization is recommended. The machine with OSC enabled updates the contacts in the mailbox, causing a change for our sync program to consider, and then the item is updated, as per the relationship settings.  This "ping pong" effect takes time to go through. Systems with OSC on can take an hour to sync, while when it is turned off, that same relationship can sync in under a minute.

365 Installations
Enabling this is the new normal for the changing 365 environments - Social Connector control for clients using Office 365 configuration policy

Go directly to the link provided as your Tenant or Global Admin https://config.office.com/officeSettings/officePolicies 
This link can be navigated to from the main Office Portal, by selecting all Admin Centers and the option “Office configuration”, which directs to the Microsoft 365 Apps Admin Center.  Again, log in as the Global or Tenant Admin to create or confirm the policy,  Name it "Disable OSC", and you can apply it to "all users" or create a new security group called something like [zDisable_OSC] and include in the group at least the source mailboxes and any user who opens the source mailbox. 
When making the policy, when prompted for the actual policy name, search for the term "Social"  and then select the option "Turn off Outlook Social Connector and enable and activate the policy. 

Usually most organizations set to apply this policy to all users since the OSC can be a time waster, but it is crucial to turn off for at least the source mailbox.  Again many companies do this for all users but if you do not, confer with your Diditbetter Software Representative to enable "Ignore Destination item changes" in the template relationships.  If you are being directed here by your Support Engineer, and we have access to the replication server, we have already set this option for you. 

More information can be found on https://techcommunity.microsoft.com/t5/office-365-blog/the-new-cloud-based-policy-management-service-for-office-365/ba-p/480676

On Premises local AD Group Policy

• Create the Group Policy "the Microsoft way" for most all configurations. 
• Disable Outlook Social Connector by Group Policy

After completion and applying these Policies, this completes the configuration and optimize Contact Synchronization

 

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

https://support.apple.com/kb/PH2613?locale=en_US

https://support.apple.com/kb/PH11573?viewlocale=en_US&locale=en_US

https://support.apple.com/kb/PH11568?viewlocale=en_US&locale=en_US

Disable iCloud with group policy (GP) as per tip above

Disable iCloud sync for calendars on mobile devices – often this is a breach of security anyway

For recurring items, never allow a no end date and fix this by GP

Suggest putting Birthdays in sub-calendar