Summary: Synchronization issues between Outlook and Outlook Web App can lead to outdated mailboxes and discrepancies between the Outlook client and OWA. It also prevents Outlook users from sending or receiving new emails on Outlook clients. In this post, we discussed reasons for synchronization issues between Outlook and Outlook Web App, solutions to fix them.
Outlook client and Outlook Web App (OWA) are two different modes to access Exchange or Microsoft 365 email accounts.
Outlook for Windows creates an Outlook data file, such as OST, to store a copy of mailbox items on the local machine. Offline Storage Table or OST (also known as Offline Folder) allows users to access their Outlook account and mail items even when the system is offline. The changes made in the Outlook client are first stored in the OST file and then synched with the Exchange or mailbox server based on the Outlook settings.
On the other hand, Outlook Web App or OWA runs on a compatible web browser, such as Google Chrome, and connects to the mailbox server directly. All the changes are made directly on the mailbox server, and thus, changes are updated in real-time.
However, when the Outlook client fails to synchronize the changes stored in the Outlook data file or OST with the mailbox on the server, the changes are not reflected in the OWA. This can lead to discrepancies in the number of mail items or changes between Outlook client and Outlook Web App.
Besides, synchronization issues in Outlook can lead to problem in sending or receiving new emails, inaccessible or inoperable Outlook account, and outdated mail folders.
Synchronization issues between Outlook and Outlook Web App is a common problem that usually occurs due to damaged Outlook data files (.OST). However, it may also occur due to various other reasons such as,
Following are the symptoms indicating synchronization issues between Outlook and OWA,
Follow these solutions to troubleshoot and fix synchronization issues between the Outlook client and OWA.
An unreliable or poor network connection can prevent Outlook clients from synchronizing the OST file to the mailbox on Exchange or Microsoft 365 Server. Reconnect the Ethernet cable or Wi-Fi and verify Exchange Server is online and you can access the internet. Also, check your firewall settings to prevent Outlook clients from connecting to the server and synchronizing the OST file with the mailbox server.
The Sync Issues folder contains the synchronization logs that can help you troubleshoot the synchronization issues between Outlook and Outlook Web App (OWA).
However, Sync Issues and its subfolders are not visible by default. To view these folders,
This will display the Sync Issues folder and its three subfolders.
Contains mail items that could not be sent to the mailbox server from the local Outlook data file, i.e., OST.
Contains multiple copies of conflicting mail items in the mailbox.
Contains mail items that could not be synchronized with the mailbox server. If you can’t see mail items in OWA, check this folder in the Outlook client.
Delete the mail items from Sync Issues and its subfolders and restart Outlook. Wait for the auto-synchronization to start. If you still see new logs or mail items in Sync Issues or its subfolders, follow the next solutions to fix the synchronization issue.
You may start manual sync by pressing the F9 key while Outlook is open. The changes in the OST file will be synced with the mailbox on the Exchange or Microsoft 365 server.
You may also click the ‘Update Folder’ option under the ‘Send/Receive’ tab to manually synchronize the changes stored locally in the OST file to the mailbox server. After successful synchronization, OWA should reflect the changes and updates.
If this works, check enable the auto-sync setting to fix this issue permanently.
The steps to enable auto-synchronization between Outlook and OWA are as follow,
You can use the Inbox Repair Tool or SCANPST.EXE to repair the OST file errors that might fix Outlook and OWA synchronization issues. The steps are as follow,
If the manual or auto sync fails to fix the synchronization issues between Outlook and OWA, it indicates a problem with the Outlook data file (OST). To fix this, you can rebuild a new OST file. The steps are as follow,
Outlook will start the synchronization process and download the mail items from the mailbox on the Exchange Server to this newly created OST file. This should fix the problem.
However, if there are missing items in your mailbox or Outlook, convert the backup OST file to PST using Stellar Converter for OST and then import the converted PST to your new OST file via Outlook Import Export wizard.
The tool also comes in handy when OST file rebuild fails due to the disabled or deleted mailbox from the Exchange Server or Microsoft 365. The software can also help you move mailbox items from an inaccessible or orphaned OST file directly to Live Exchange Server or Microsoft 365.
Read More, How to import OST to Office 365
Synchronization issues between Outlook and OWA can cause mismatches and discrepancies in the mail items. When Outlook fails to synchronize the mail items from the local Outlook cache (OST), it may display send/receive errors that prevent users from sending or receiving new mail items. In this blog, we discussed various solutions that you may apply to fix the synchronization issue between OWA and Outlook clients.
For more help related to Outlook or Outlook data files, such as OST to PST, leave a comment or reach us via the Self Help and Support page.
Ravi Singh is a Senior Writer at Stellar®. He is an expert Tech Explainer, IoT enthusiast, and a passionate nerd with over 7 years of experience in technical writing. He writes about Microsoft Exchange, Microsoft 365, Email Migration, Linux, Windows, Mac, DIY Tech, and Smart Home. Ravi spends most of his weekends working with IoT (DIY Smart Home) devices and playing Overwatch. He is also a solo traveler who loves hiking and exploring new trails.
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