There is a special kind of frustration in reading an email on your phone, then finding it still marked unread on your laptop an hour later. When you are dealing with outlook not syncing, your devices stop agreeing with each other: new messages appear on one device but not another, sent items vanish, or the same folder shows different contents depending on where you look.
Sync problems have many causes — a flipped offline switch, a corrupted local data file, an expired login token, or simply an outdated app — and the right fix depends on which device is misbehaving. This guide walks you through every common outlook not syncing scenario on desktop, web and mobile, with the fastest fix first in each section so you can get your inbox agreeing with itself again.
Before diving in, rule out the obvious: check that you have an internet connection and that Microsoft’s services are not having an outage. If other apps load fine and webmail works, the outlook not syncing problem is local to your device or account, and the fixes below will sort it.
Why Outlook Stops Syncing
Outlook keeps a local copy of your mailbox and constantly compares it with the server. Anything that interrupts that conversation — on your device, on your network, or on the server — produces an outlook not syncing situation. The most common causes are:
- Offline mode is on. Outlook has a “Work Offline” switch that pauses all syncing. It is easy to trigger accidentally and easy to overlook.
- Network or VPN issues. A weak connection, a VPN that routes traffic oddly, or a captive portal (hotel or café Wi-Fi) can silently block the sync channel.
- Corrupted local data files. On Windows, Outlook stores your mailbox in an OST file. If it becomes damaged, syncing stalls or loops without ever finishing.
- Expired sign-in or authentication token. Password changes, security policies, or multi-factor authentication hiccups can leave Outlook signed in but unable to sync.
- Outdated app. Old Outlook builds sometimes use sync protocols the server no longer supports, particularly after Microsoft retires legacy authentication.
- Oversized mailbox or cache. A mailbox with tens of thousands of items, or a cache set to download everything, can overwhelm the sync engine.
- Add-ins and security software. Third-party add-ins and aggressive antivirus scanning can intercept or slow the sync process.
Typical symptoms of outlook not syncing include folders that stop updating, the status bar stuck on “Trying to connect” or “Disconnected”, sent messages that never appear in Sent Items on other devices, and calendar changes that refuse to propagate. Identifying your symptom points you at the right section below.
How to Fix Outlook Not Syncing on Desktop
The desktop app is where most outlook not syncing complaints start, because it keeps the largest local copy of your mailbox. Work through these fixes in order.
Check Your Connection and Switch Off Offline Mode
Look at the status bar at the bottom of the Outlook window. If it says “Working Offline” or “Disconnected”, click the Send/Receive tab and make sure “Work Offline” is not highlighted. This single toggle is the cause of a remarkable number of outlook not syncing reports — especially on laptops where it can be triggered by a stray click or a function-key shortcut.
If Outlook shows “Trying to connect” for more than a minute, test your connection: open a website in your browser and, if you use a VPN, temporarily disconnect it and try syncing again. Corporate VPNs and hotel Wi-Fi portals are frequent silent blockers. A quick restart of Outlook after the network stabilises often clears the backlog.
Rebuild the OST File with a Fresh Profile
If Outlook connects but folders never finish updating, the local OST data file is probably damaged. The cleanest fix is a new profile, which forces Outlook to rebuild everything from the server. Go to Control Panel > Mail > Show Profiles, click Add, name the new profile, and add your account to it. Set the new profile as the default and restart Outlook.
Do not worry about losing mail: with IMAP, Exchange, or Microsoft 365 accounts, everything lives on the server and simply re-downloads. This step resolves the majority of stubborn outlook not syncing cases on Windows where the status bar spins forever. If you also see repeated credential prompts alongside the sync failure, our guide to fixing Outlook pii email errors covers the profile repairs that break those loops.
Repair Your Outlook Data Files
Before rebuilding a profile, you can try repairing the existing data file. Close Outlook, then run the Inbox Repair tool (scanpst.exe), which lives in your Office installation folder. Point it at your OST or PST file, let it scan, and allow it to repair any errors it finds. Then reopen Outlook and watch the status bar — a successful repair usually resumes syncing within a few minutes.
For Microsoft 365 and Exchange accounts, an alternative is to reduce the cached mail window: go to File > Account Settings > Account Settings, select the account, click Change, and drag the “Mail to keep offline” slider from All down to 12 or 6 months. A smaller local cache syncs faster and is far less likely to corrupt. This is especially effective when outlook not syncing only affects older folders while recent mail arrives fine.
Update Outlook and Review Account Settings
An outdated Outlook build can lose the ability to sync when Microsoft retires older authentication methods — which has happened several times in recent years. In classic Outlook, go to File > Office Account > Update Options > Update Now, then restart your computer so the update takes full effect.
While you are in the account settings, verify that the account type is correct (Exchange or Microsoft 365 accounts should not be set up as plain IMAP if you want full syncing of calendar and contacts) and that the email address has no typos. If your organisation recently changed a password policy or enabled multi-factor authentication, remove the account and add it again so Outlook picks up the new sign-in flow — stale tokens are a classic hidden cause of outlook not syncing on work accounts.
How to Fix Outlook Not Syncing on the Web
Outlook on the web (outlook.com or your organisation’s webmail) has no local data file to corrupt, so an outlook not syncing problem here is almost always about the browser or the session. Start with the simplest step: press Ctrl+Shift+R (Cmd+Shift+R on Mac) to hard-refresh the page, bypassing the browser cache.
If a hard refresh does not help, sign out of your Microsoft account completely, clear the browser’s cache and cookies for the Outlook site, and sign back in. Browser extensions — particularly ad blockers, privacy tools, and script managers — can interfere with Outlook’s sync scripts, so try an Incognito or private window with extensions disabled. If Outlook on the web syncs fine in the private window, disable extensions one by one in your normal window until you find the culprit.
Also try a different browser. If Edge syncs but Chrome does not (or vice versa), the problem is isolated to one browser’s stored data, and clearing that browser’s full cache or resetting its settings will fix it. And if outlook not syncing affects webmail on every browser and device, check Microsoft’s service status page or ask your IT team — a server-side incident means the only fix is patience.
How to Fix Outlook Not Syncing on Mobile
Mobile sync failures usually come down to the app’s background permissions or a stale account configuration. The fixes differ slightly between the Outlook mobile app and built-in mail apps, so match the steps to what you use.
Remove and Re-add the Account
In the Outlook mobile app, tap your profile icon > Settings (gear) > select the account > Delete Account. Then add it again from scratch. Re-adding forces a fresh authentication token and a clean initial sync, and it resolves most outlook not syncing cases on phones where mail arrives late or not at all.
If you use your phone’s built-in mail app instead of the Outlook app, consider switching: the official Outlook app handles Microsoft’s modern authentication far more reliably than generic mail clients, and many “my iPhone mail won’t sync” problems disappear the moment people move to it. After re-adding, give the first sync several minutes on Wi-Fi — large mailboxes take a while to populate.
Check Sync Settings and Permissions
On Android, open Settings > Apps > Outlook > Mobile data and make sure “Allow background data usage” is on, then check Battery settings and set Outlook to “Unrestricted” so battery optimisation does not kill background syncing. Aggressive power-saving modes are the number one cause of outlook not syncing on Android — the app simply never gets a chance to check for mail.
On iPhone and iPad, go to Settings > General > Background App Refresh and make sure it is enabled for Outlook. Then open the Outlook app’s own settings and confirm that sync is enabled for Mail, Calendar, and Contacts, with the sync period set to something sensible like the last month rather than “All time”, which can choke the initial download. Also check that Focus modes or Do Not Disturb schedules are not silencing the notifications that would tell you mail has arrived.
Update the App and Restart the Device
An outdated Outlook app can stop syncing after server-side changes, just like on the desktop. Update Outlook from the Play Store or App Store, then restart your phone — a restart clears stuck background services that an update alone sometimes cannot. If problems persist after the update, check your phone’s date and time settings: authentication tokens fail when the device clock is wrong, so leave “Automatic date and time” switched on.
As a last resort on mobile, uninstall and reinstall the Outlook app entirely. This clears every cached credential and setting in one move. It takes a few minutes to set up again, but it fixes the small residue of outlook not syncing cases that re-adding the account alone does not.
Quick Reference: Outlook Not Syncing by Device
Find your device below for the most likely cause and the first fix to try. If that fix does not work, work through the full section for your device above.
| Device | Most common cause | First fix to try |
|---|---|---|
| Windows desktop (classic Outlook) | Corrupted OST file or Offline mode on | Switch off Work Offline; create a new mail profile |
| Windows (new Outlook) | Stale account or outdated app | Remove and re-add the account; update via the Store |
| Mac (Outlook) | Expired sign-in token | Sign out and sign back in; update the app |
| Outlook on the web | Browser cache or a blocking extension | Hard refresh; retry in a private window |
| Android (Outlook app) | Battery optimisation killing background sync | Set battery usage to Unrestricted; allow background data |
| iPhone / iPad (Outlook app) | Background App Refresh off; outdated app | Enable Background App Refresh; update the app |
When to Rebuild Your Outlook Profile
Most outlook not syncing problems are fixed by the steps above, but some need the nuclear option: a completely fresh profile. Rebuild your profile when you see any of these signs:
- Sync errors persist after repairing the data file and updating the app.
- Outlook crashes or freezes every time it tries to synchronise a particular folder.
- The same account syncs perfectly on webmail and mobile but never on one desktop.
- You have recently changed email providers, domains, or authentication methods and the old profile keeps using stale settings.
On Windows, go to Control Panel > Mail > Show Profiles > Add, create the new profile, add your account, and set it as the default. Keep the old profile for a day or two in case you need to check an old setting, then delete it. Because Exchange, Microsoft 365, IMAP, and Outlook.com accounts all keep the master copy on the server, rebuilding is safe — your mail, calendar, and contacts simply download again.
One caution: if you use POP3, mail may live only on your computer, so back up the PST file before touching the profile. Better still, consider this the moment to switch that account to IMAP, which syncs properly across devices. If your trouble is specifically with messages refusing to send during sync, our guide to Outlook send and receive errors covers the Outbox side of the problem, and if Outlook feels sluggish overall, learn how to clear the Outlook cache for a quick performance tidy-up.
Frequently Asked Questions
Why is my Outlook not syncing emails on my phone but works on my computer?
This usually means the desktop is fine and the phone’s app is being throttled or holds a stale login token. On Android, set Outlook’s battery usage to Unrestricted and allow background data; on iPhone, enable Background App Refresh for Outlook. If that does not help, delete the account from the Outlook mobile app and add it again — a fresh token fixes most one-device outlook not syncing cases.
How do I force Outlook to sync right now?
On desktop Outlook, go to the Send/Receive tab and click “Send/Receive All Folders”, or press F9. In the new Outlook for Windows, click the sync/refresh icon in the folder pane. On mobile, pull down on the inbox list to trigger a manual refresh. If a manual sync spins without finishing, the underlying outlook not syncing cause — usually a damaged OST or a network block — still needs the fixes above.
Will I lose my emails if I create a new Outlook profile?
No — not with Exchange, Microsoft 365, Outlook.com, or IMAP accounts, because the master copy of your mail lives on the server and simply downloads again into the fresh profile. The only exception is POP3, which can keep mail solely on your computer; back up the PST file first if you use POP3. Rebuilding the profile is one of the safest and most effective fixes for a persistent outlook not syncing problem.
Why does Outlook say “Disconnected” or “Trying to connect”?
“Disconnected” almost always means Work Offline mode is switched on — turn it off from the Send/Receive tab. “Trying to connect” means Outlook cannot reach the server: check your internet connection, disconnect any VPN temporarily, and make sure your firewall allows Outlook. If webmail works but the desktop app stays stuck, your network is fine and the app’s profile or data file needs the repair steps in this guide.
How often should Outlook sync by default?
With Exchange, Microsoft 365, and Outlook.com accounts, syncing is effectively continuous — changes push within seconds. IMAP accounts check on a schedule you can customise under Send/Receive Groups (every 5–10 minutes is a sensible default). If you notice delays, check that you have not set an unusually long interval and that your device is not pausing background activity to save battery.
Can a full mailbox stop Outlook from syncing?
Yes. A mailbox near its quota — or a local cache holding tens of thousands of items — can slow syncing to a crawl or stop it entirely. Archive old mail, empty Deleted Items and Junk, and reduce the “Mail to keep offline” slider to 12 months or less. A leaner mailbox syncs faster, corrupts less often, and makes every other fix in this guide more likely to work first time.