Outlook randomly not syncing new emails unless I force refresh

Question

Outlook randomly not syncing new emails unless I force refresh

garwin clark 0

My inbox just sits there and doesn’t pull new emails until I manually hit refresh. No errors, internet is fine, and it happens on both desktop and mobile. Cached mode is on. Not sure if this is some weird sync delay, Autodiscover hiccup, or something server-side. Any ideas what to check next?

Gareth Jones 0 Reputation points

2026-04-20T08:48:49.07+00:00

I'm hearing similar issues - since last week for some users who use Outlook online the site indicates there are new emails but they do not show in the inbox. If you filter for unread they show but remove the filter and they do not. Manually refreshing the page shows them. This is happening on multiple devices for the same user so would appear to be a mailbox based issue. I know this is not helpful to you Garwin, but might give Microsoft some more information as to current issues.
Wes Purdy 0 Reputation points

2026-04-30T00:28:40.61+00:00

I am having similar issues in my work environment with multiple users and multiple email accounts. Our issues are with the classic version of outlook. With cache turned on, emails do not come through but are searchable in the outlook app. All emails are visible on the Outlook on the Web. Turning off cache in the outlook app seems to fix the syncing issues (emails come through on-time), but outlook runs really slow. Re-starting the outlook app also re-syncs and shows the latest (missed) emails but subsequent ones do not come through. Re-building the OST file does not fix. Building a new outlook profile does not fix. Due to the recent timing of both Garwin and Gareths issues, and our own, I'm wondering if it's a more wide spread issue as Gareth mentioned above.
Hani-Ng 10,575 Reputation points Microsoft External Staff Moderator

2026-05-05T23:47:43.32+00:00

Hi Wes Purdy

Since this introduces a different scenario with a separate set of requirements from the original question, I recommend creating a new thread and including your specific details there. This helps avoid mixing multiple issues in one discussion and allows moderators to focus on your use case more effectively.

Creating a separate thread will also enable us to request additional information via private message if needed, while helping protect personal or organizational data.

If needed, you can submit a support ticket to reach out to the Microsoft Support team via the Admin Center. More details on how to get help from Microsoft 365 support can be found here: Get support - Microsoft 365 admin | Microsoft Learn.

Thank you for your understanding.

2 answers

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Gareth Jones 0 Reputation points

2026-04-20T08:48:49.07+00:00

I'm hearing similar issues - since last week for some users who use Outlook online the site indicates there are new emails but they do not show in the inbox. If you filter for unread they show but remove the filter and they do not. Manually refreshing the page shows them. This is happening on multiple devices for the same user so would appear to be a mailbox based issue. I know this is not helpful to you Garwin, but might give Microsoft some more information as to current issues.
Wes Purdy 0 Reputation points

2026-04-30T00:28:40.61+00:00

I am having similar issues in my work environment with multiple users and multiple email accounts. Our issues are with the classic version of outlook. With cache turned on, emails do not come through but are searchable in the outlook app. All emails are visible on the Outlook on the Web. Turning off cache in the outlook app seems to fix the syncing issues (emails come through on-time), but outlook runs really slow. Re-starting the outlook app also re-syncs and shows the latest (missed) emails but subsequent ones do not come through. Re-building the OST file does not fix. Building a new outlook profile does not fix. Due to the recent timing of both Garwin and Gareths issues, and our own, I'm wondering if it's a more wide spread issue as Gareth mentioned above.
Hani-Ng 10,575 Reputation points Microsoft External Staff Moderator

2026-05-05T23:47:43.32+00:00

Hi Wes Purdy

Since this introduces a different scenario with a separate set of requirements from the original question, I recommend creating a new thread and including your specific details there. This helps avoid mixing multiple issues in one discussion and allows moderators to focus on your use case more effectively.

Creating a separate thread will also enable us to request additional information via private message if needed, while helping protect personal or organizational data.

If needed, you can submit a support ticket to reach out to the Microsoft Support team via the Admin Center. More details on how to get help from Microsoft 365 support can be found here: Get support - Microsoft 365 admin | Microsoft Learn.

Thank you for your understanding.

Answer 1

Hi garwin clark

Firstly, you can try checking Outlook on the Web (OWA) connects directly to your mailbox

Open a private/incognito browser window > go to OWA > sign in. Keep this window open and send a test email to your account. Observe if the new email appears instantly in OWA or if there is also a delay.

If OWA works correctly (instant delivery): The problem is with how your desktop and mobile clients are communicating with the server.

Create a New Outlook Profile: A corrupt profile can cause a wide range of sync issues. This step creates a fresh connection and a new local cache (.OST file) without deleting your old profile or any server data. You can see detailed information: Create an Outlook profile - Microsoft Support
Check "Work Offline" Status: In Outlook, go to the Send / Receive tab > Ensure the "Work Offline" button is not active. For good measure, click it on and then off again to reset the connection state. Verify Send/Receive Settings:
On the Send / Receive tab, click Send/Receive Groups > Define Send/Receive Groups > Ensure that "Schedule an automatic send/receive every..." is checked and set to a reasonable time (ex: 10 minutes). While Cached Mode uses push email, this setting can sometimes interfere.

If OWA is also delayed: The problem is almost certainly on the server-side with your mailbox.

You can try to run the Outlook Connectivity Test - This web-based tool checks the external connectivity that Outlook relies on, including Autodiscover.

Go to the Microsoft Remote Connectivity Analyzer > Select the "Outlook Connectivity" test.
Enter your credentials and run the test. A "Success" result is expected; any failures will provide specific errors that are key to diagnosing the problem.

Please try this step first by testing Outlook on the Web (OWA) and share your results so I can better understand what’s happening.

I hope this information is helpful, and I look forward to hearing from you.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Hani-Ng 10,575 Reputation points Microsoft External Staff Moderator

2026-04-21T03:00:08.37+00:00

Hi garwin clark

I just wanted to quickly check in to see if you have any updates or need any additional information. Please feel free to let me know!

Answer 2

Start with basic connectivity and sync checks, then address cached mode and folder state.

Confirm connectivity and basic sync

Make sure the client is actually online, not in “Working Offline” or “Disconnected” state.
In Outlook, use the Sync button on the View tab to force a manual sync and watch the status bar for any sync-related messages. For more detail, see Sync to manually check for new mail and to send messages in Outlook.

Fix issues specific to Cached Exchange Mode If the problem is that new items exist in the mailbox but don’t appear in the cached Inbox until a manual refresh, the cached store may be stuck:

Exit Outlook.
Start Outlook with the /cleanips switch to clear the incoming item processing pipeline:
```
  Outlook.exe /cleanips
```
This clears the hidden ItemProcSearch processing state that can prevent new items from being unhidden in the Inbox.

If that does not help:

Start Outlook normally.
Right-click the Inbox folder → Properties → General tab.
Select Clear Offline Items → OK when prompted that data was removed from the .ost.
With Inbox selected, press Shift+F9 to force resynchronization of that folder.

Address broader cached-mode sync failures If changes made while Outlook is closed (for example, by server-side processes or archiving/EWS-based tools) are not syncing correctly when Outlook reopens, the cached .ost may have sync state issues:

For any folder showing sync problems, right-click the folder → Properties → General → Clear Offline Items, then Shift+F9 to resync.
If problems are widespread, consider temporarily switching the profile to Online mode to confirm that server-side mail flow and Autodiscover are healthy. If online mode works consistently, recreate the cached profile and .ost.

Check for client-side filters or views If mail appears “late” or only after refresh, verify that:

The Inbox view is set to show Today (not a past date) and that no custom filter is hiding recent items.
No rules are silently moving new mail to other folders (including RSS or custom folders).

If, after these steps, online mode shows immediate delivery but cached mode continues to lag or require manual refresh, recreate the Outlook profile and .ost and test again. If both online and cached modes show delay, investigate server-side transport or mobile client configuration in Exchange Online.

References:

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Outlook randomly not syncing new emails unless I force refresh

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