Outlook 365 can stop updating for several different reasons: Outlook may be offline, the account may need to be authenticated again, an Outbox message may be blocking delivery, or the local Outlook profile may be damaged. The correct fix depends first on which Outlook app you are using.
New Outlook for Windows has a Sync command under View. Classic Outlook for Windows uses the Send/Receive tab. The instructions below identify the edition before suggesting repairs.
1. Identify your Outlook edition
| Edition | Manual sync command | Offline settings |
|---|---|---|
| New Outlook for Windows | Mail → View → Sync | Settings → General → Offline |
| Classic Outlook for Windows | Send/Receive → Send/Receive All Folders | Send/Receive → Work Offline |
Both editions use F9 to start a manual sync. In new Outlook, a status message appears at the bottom of the message list. Do not follow instructions telling you to find a Send/Receive tab in new Outlook; that tab was replaced by Sync.
2. Force a manual sync
New Outlook
- Select Mail on the navigation bar.
- Open View.
- Select Sync, or press F9.
- Watch the status message at the bottom of the message list.
Classic Outlook
- Open the Send/Receive tab.
- Select Send/Receive All Folders, or press F9.
To synchronize only one account in classic Outlook, choose Send/Receive → Send/Receive Groups, point to the account, and select Inbox.
#1 Best Overall
- All-day Comfort: The design of this standard keyboard creates a comfortable typing experience thanks to the deep-profile keys and full-size standard layout with F-keys and number pad
- Easy to Set-up and Use: Set-up couldn't be easier, you simply plug in this corded keyboard via USB on your desktop or laptop and start using right away without any software installation
- Compatibility: This full-size keyboard is compatible with Windows 7, 8, 10 or later, plus it's a reliable and durable partner for your desk at home, or at work
- Spill-proof: This durable keyboard features a spill-resistant design (1), anti-fade keys and sturdy tilt legs with adjustable height, meaning this keyboard is built to last
- Plastic parts in K120 include 51% certified post-consumer recycled plastic*
If Sync or Send/Receive produces no new mail, continue with the connection checks below. A manual command cannot repair an account that is disconnected or incorrectly configured.
3. Check whether Outlook is offline
In classic Outlook, look at the status bar at the bottom of the window. Messages such as Disconnected, Working Offline, or Trying to connect… mean Outlook cannot reach the mail server.
- Open the Send/Receive tab.
- If Work Offline is highlighted, select it to return Outlook to online mode.
- Wait for the status to change, then select Send/Receive All Folders.
- If a message remains in the Outbox, reopen it and select Send again.
A clear, unhighlighted Work Offline button indicates that classic Outlook is online. If the button is missing for an Exchange or Microsoft 365 account, Cached Exchange Mode may be disabled.
Also check the basics: open a website, temporarily disconnect and reconnect the network, and try Outlook on the web. If Outlook on the web also fails, the problem is more likely to be the account, service, or mailbox rather than the Windows application.
The Tool Desk
Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →4. Reauthenticate the account
If the account password was changed through a provider’s website, Outlook may continue using the old credentials.
- In new Outlook, select the icon beside the account name.
- Select Continue.
- Complete the sign-in prompts, including multifactor authentication if requested.
- Run View → Sync again.
Some providers require an app password rather than the normal account password, particularly when two-step verification is enabled.
For a Hotmail.com or Live.com address in classic Outlook, check that the account type is Outlook.com, not Exchange or Microsoft 365. The wrong account type can prevent existing messages and custom folders from appearing.
For an IMAP account that never prompts for a password, open its IMAP account details and make sure Require logon using Secure Password Authentication (SPA) is unchecked.
Rank #2
- KEYBOARD: The keyboard works for Windows with hot keys that enable easy access to Media, My Computer, Mute, Volume up/down, and Calculator
- EASY SETUP: Experience simple installation with the USB wired connection
- VERSATILE COMPATIBILITY: This keyboard is designed to work with multiple Windows versions, including Vista, 7, 8, 10 offering broad compatibility across devices.
- SLEEK DESIGN: The elegant black color of the wired keyboard complements your tech and decor, adding a stylish and cohesive look to any setup without sacrificing function.
- FULL-SIZED CONVENIENCE: The standard QWERTY layout of this keyboard set offers a familiar typing experience, ideal for both professional tasks and personal use.
5. Check the Outbox for a blocked message
A single large or damaged message can prevent that message and later messages from being sent. Open the oldest message in the Outbox first.
- Open Outbox.
- Open the oldest message that is still waiting.
- Remove its attachment, replace it with a smaller file, or upload the file and send a sharing link.
- Save the message, delete it, or send it again.
- Run a manual sync.
Classic Outlook guidance specifically flags attachments larger than 20 MB. Outlook.com has a separate limit: a message containing an attachment larger than 25 MB cannot be sent. Mailbox or provider limits may be lower.
If sending and receiving stopped immediately after antivirus software reported a threat, the antivirus email-scanning component may be blocking mail traffic. Update the security software and check its quarantine or email-protection settings before testing again.
6. Check offline synchronization settings
Classic Outlook: Cached Exchange Mode
Cached Exchange Mode stores a local copy of recent mailbox data and is recommended for Microsoft 365 accounts. Classic Outlook synchronizes 12 months of email by default, so older messages may exist on the server without being available in the local cache.
To change the period:
- Go to File → Account Settings → Account Settings.
- On the Email tab, select the Exchange or Microsoft 365 account.
- Select Change.
- Under Offline Settings, move the slider to the required period.
- Restart Outlook when prompted.
Available choices commonly include All, 12 months, 6 months, 3 months, and 1 month. Outlook 2016 can also offer as little as 3 days. Increasing the period uses more disk space and can make Outlook take longer to start. Microsoft recommends only one month of synchronized data in virtual-desktop environments.
New Outlook: offline email scope
New Outlook normally enables offline access. To verify it, open Settings → General → Offline, enable Enable offline email, calendar, and people, and select Save.
The same page controls which folders and how many days are kept locally:
- Folders to save: Default, Default and favorites, or Default, favorites, and recently used.
- Days of email to save: 7, 30, 90, or 180 days. The default is 30 days.
If local storage is insufficient, Outlook may save fewer items or disable offline access. Offline mode also does not provide every online feature. For example, new Outlook currently limits adding attachments or inline images to drafts, changing individual calendar events, changing email sort order, viewing the Other inbox when Focused Inbox is enabled, and changing notification, signature, or calendar settings.
Recommended Free Tools
Rank #3
- Durable and Reliable: This USB keyboard features a curved space bar, spill-resistant design (2), durable keys that can withstand 10 million keystrokes, and sturdy, adjustable tilt legs
- Comfortable, Familiar Typing: You’ll enjoy a comfortable and familiar typing experience thanks to the deep-profile keys and standard layout with full-size F-keys and number pad
- Full-size Sculpted Mouse: The high-definition optical USB mouse puts comfort and control in your hands with smooth, accurate tracking and an ambidextrous shape that feels good hour after hour
- Simple Set-Up: Simply plug the keyboard and mouse into the USB ports on your desktop, laptop, or netbook and you're ready to work; compatible with Windows 7, 8, 10 or later
- Clear and Convenient: The bold, bright white and long-lasting characters make the keys on this PC or laptop keyboard easy to read and extra durable
7. Repair the classic Outlook profile
If the account works in Outlook on the web but classic Outlook still will not synchronize, repair the profile.
- Go to File → Account Settings → Account Settings.
- Open the Email tab.
- Select the affected account.
- Select Repair and complete the wizard.
- Restart Outlook and run Send/Receive All Folders.
The Repair option is unavailable in Outlook 2016 when it connects to an Exchange account. In that case, test with a new profile instead.
8. Test Outlook without add-ins
Add-ins can interfere with authentication, folder updates, or sending. Start classic Outlook in Safe Mode:
- Press Windows key + R.
- Enter
Outlook /safe. - Select OK.
- Try to synchronize and send a test message.
If mail works in Safe Mode, disable COM add-ins:
- Go to File → Options → Add-ins.
- At the bottom, set Manage to COM Add-ins.
- Select Go.
- Clear the check boxes and select OK.
- Restart Outlook.
Re-enable add-ins one at a time, restarting Outlook after each change. This identifies the problematic add-in. Disable an add-in rather than selecting Remove; Remove can delete it if you have administrator rights.
Quick wins for a faster PC:
Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →9. Create a new profile or repair the data file
A damaged profile can cause repeated synchronization failures even when the mailbox and credentials are valid. Create a new profile and use it as a test:
- Create a new Outlook profile through the Windows Outlook profile settings.
- Close Outlook.
- Hold Shift while starting Outlook.
- In Choose Profile, select the new profile and choose OK.
- Check whether mail synchronizes normally.
If the new profile works, the original profile is the likely cause. Removing an old profile deletes its offline cached content, so back up any required data files first.
For suspected data-file corruption, use the Inbox Repair Tool, scanpst.exe. It can check and repair Outlook .pst and .ost data files. Close Outlook before running the tool, select the relevant file, and follow the repair wizard.
If the classic Outlook navigation pane is corrupted, close Outlook, press Windows key + R, enter the exact command Outlook.exe /resetnavpane, and select OK. This resets navigation-pane customizations; it is not a mailbox resynchronization command.
Free tools Windows power users keep installed
One-click scans. No signup required.
Rank #4
- A plug-and-play USB connection with Low-profile keys give you a quiet, comfortable typing experience
- Simple Wired USB Connection,You will enjoy a comfortable and quiet typing experience
- The keyboard for business and office working is the budget-friendly keyboard that is built for longer use
- Low profile keys for a more comfortable and quiet keystroke, desktop-centric design, splash resistant
10. Check Outlook.com-specific causes
If the account is Outlook.com, synchronization may be working while messages are being filtered or rejected elsewhere.
- Check the Other tab, Junk Email, inbox rules, forwarding, and filters.
- To correct message order, select Filter → Sort → Date.
- Check Microsoft cloud storage. When it is full, Outlook.com cannot send or receive mail. Messages sent while storage was full are bounced to the sender and cannot be recovered.
For Gmail, Yahoo, iCloud, POP, or IMAP accounts, Outlook does not provide the same manual Sync capability available for Microsoft accounts. The provider must support modern authentication and IMAP for connected use. Microsoft also recommends disabling active POP and IMAP at the provider and retrying when a connected-app problem persists.
If only one phone or tablet fails while other devices work, remove the partnership between that mobile device and the mailbox, then add or sync the account again.
11. Allow for normal synchronization behavior
Not every apparent discrepancy is data loss. When classic Outlook works offline, it can record a local move or deletion that conflicts with a server-side change made during the same period. After reconnection, an item deleted on the Exchange server may reappear if the offline client moved that item locally. Outlook may also recreate an item in a destination folder when it synchronizes a move after the server copy has already been deleted.
Give the client time to finish synchronization before moving or deleting the same message repeatedly on different devices. Compare the mailbox in Outlook on the web to determine whether the item exists on the server or only in the local cache.
12. Configure automatic syncing in classic Outlook
Classic Outlook’s automatic send/receive interval is configured separately from the manual F9 command:
- Open Send/Receive → Send/Receive Groups → Define Send/Receive Groups.
- If you have no custom groups, select All Accounts.
- Set the automatic send/receive interval for when Outlook is offline or connected, as applicable.
- Use a value from 1 through 1440 minutes.
A very long interval can look like a sync failure. However, changing the interval will not fix an account that is offline, blocked by a bad password, or unable to authenticate.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.When to stop troubleshooting locally
If Outlook on the web also cannot send or receive, check Microsoft 365 service health through your organization’s administrator, confirm that the mailbox is not full, and contact the mail administrator or provider. If only classic Outlook fails after Safe Mode, profile repair, and a new-profile test, update or repair Microsoft 365. Note that Microsoft’s current startup guidance identifies Office 2016 and Office 2019 clients connecting to Microsoft 365 services as having reached end of support.
PC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Crashes, No Sound, or Screen Glitches?
Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteBest Value
- 【Large Print Keyboard】- 4X larger than standard keyboard fonts, clear and easy to find, and can really help those who have trouble seeing keyboards. Perfect for elderly, the visually impaired, schools, special needs departments and libraries, etc
- 【White LED Backlight】- Bright and evenly distributed backlit keys, easy typing in lower light environment. Ideal for studio work, office. Backlit can choose to turn on/off and adjust brightness.
- 【Full Size & Ergonomics Design】- Unfold the feet at back of the keyboard to reduce hand fatigue and enjoy long hours of playing. Full QWERTY English (US) 104 key keyboard layout with numeric keypad, Large Print keys provides superior comfort without forcing you to relearn how to type.
- 【Plug and Play & Wide Compatibility】 - This USB keyboard takes away the hassle of power charging or swapping out batteries and is easy to setup. No drivers required.Compatible with Windows 2000/XP/7/8/10, Vista,Raspberry Pi 3/4, Mac OS(Note: Multimedia keys may not fully compatible with Mac, OS System).Works with your PC, laptop.
- 【Spill-proof】- This durable keyboard features a spill-resistant design. So you don't have to worry about spilling coffee and water. Enjoy Keys life of more than 5000W times.
FAQ
What is the fastest way to sync Outlook 365?
In new Outlook for Windows, select Mail → View → Sync, or press F9. In classic Outlook, select Send/Receive → Send/Receive All Folders, or press F9.
Why is there no Send/Receive tab in Outlook?
You are probably using new Outlook for Windows. Microsoft replaced the Send/Receive tab with View → Sync. Send/Receive remains available in classic Outlook.
Why does Outlook say Working Offline?
Classic Outlook cannot currently reach the mail server or has been placed in offline mode. Select Send/Receive → Work Offline to return online, then run Send/Receive All Folders.
Why are old emails missing from classic Outlook?
Cached Exchange Mode synchronizes 12 months of email by default, not necessarily the entire mailbox. Increase the Offline Settings slider at File → Account Settings → Account Settings → Change.
Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsCan a full mailbox or cloud drive stop Outlook from syncing?
Yes. If Microsoft cloud storage is full, Outlook.com cannot send or receive email. Clear storage and check the mailbox again; messages bounced while storage was full cannot be recovered.
What should I do if Outlook keeps a message in the Outbox?
Open the oldest stuck message first. Remove or reduce a large attachment—classic Outlook guidance flags files over 20 MB—and send the file as a cloud link instead.
How can I tell whether an Outlook add-in is causing the problem?
Start classic Outlook with Windows key + R, enter Outlook /safe, and test mail. If synchronization works there, disable COM add-ins under File → Options → Add-ins and re-enable them one at a time.
The Bottom Line
Start with the edition-specific manual sync command, then check the connection state and Outbox. Reauthenticate the account if its password changed, verify the offline cache period, and test classic Outlook in Safe Mode. If the issue remains, repair or replace the profile and compare the mailbox with Outlook on the web. That comparison quickly shows whether the fault is in Outlook’s local cache or in the account and mail service.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
