Outlook does not have one synchronization command for every version and account type. In new Outlook for Windows and Outlook on the web, use Mail > View > Sync. In classic Outlook for Windows, use Send / Receive > Send/Receive All Folders. Both versions also support F9, but third-party accounts do not behave identically in new Outlook.
This guide covers manual syncing, automatic synchronization, offline mail storage, Outlook for Mac, mobile devices, and the most common reasons messages remain missing or stuck.
Manually sync Outlook on Windows
New Outlook for Windows
- Open Outlook and select Mail.
- Select View on the ribbon.
- Select Sync.
Outlook displays a synchronization status message at the bottom of the message list. You can also press F9 to start a manual sync.
The former Send / Receive tab belongs to classic Outlook. If you are using the newer Windows app, looking for that tab will lead you to the wrong instructions.
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Classic Outlook for Windows
- Select the Send / Receive tab.
- Select Send/Receive All Folders.
Pressing F9 performs the same all-folder send-and-receive operation.
To synchronize only one account, select Send / Receive > Send/Receive Groups > [account name] > Inbox. This is useful when several mailboxes are configured and one account is slow or unavailable.
Outlook on the web and Outlook.com
In a browser, select Mail > View > Sync, or refresh the browser page. The F9 shortcut also works in supported Outlook web views.
New Outlook’s Sync command does not provide the same manual-sync capability for third-party accounts such as Gmail, Yahoo, iCloud, generic POP, and generic IMAP. For those accounts, check the provider’s webmail service to determine whether the message has reached the mailbox, then review the account connection in Outlook.
How Outlook synchronizes automatically
When Outlook is online, it checks for new incoming and outgoing messages at startup and at intervals controlled by its account settings. Selecting Send normally sends a message automatically when the connection is available.
Change automatic send/receive timing in classic Outlook
- Select Send / Receive.
- Select Send/Receive Groups > Define Send/Receive Groups. You can also press Ctrl+Alt+S.
- Select All Accounts, unless you have created a custom send/receive group.
- Under When Outlook is Offline, select Schedule an automatic send/receive every….
- Enter an interval from 1 to 1440 minutes.
- Use the group options to choose which accounts and folders are included.
- Select Close.
The Include this group in send/receive F9 option determines whether F9 includes the group while Outlook is offline. It does not change the normal online schedule.
Enable offline email in new Outlook
New Outlook can save mail, calendar, and people data locally so you can work while disconnected. It must be enabled before offline access is available.
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- Select Settings.
- Go to General > Offline.
- Turn on Enable offline email, calendar, and people.
- Select Save.
Choose the folders Outlook saves
Under Settings > General > Offline > Folders to save, choose one of these options:
| Option | Local folders included |
|---|---|
| Default | Inbox, Sent, Drafts, Archive, Deleted, and Snoozed |
| Default and favorites | The default folders plus folders marked as favorites. This is the default selection. |
| Default, favorites, and recently used | The default folders, favorites, and recently used folders |
Choose how much email is stored locally
Under Settings > General > Offline > Days of email to save, select 7, 30, 90, or 180 days. The default is 30 days.
This setting affects the local copy, not the mailbox on the server. Older messages remain available online, but they may not be readable without an internet connection. If the computer does not have enough storage, Outlook may save fewer items or disable offline access.
Adjust offline storage in classic Outlook
For Exchange and Microsoft 365 accounts using Cached Exchange Mode:
- Select File > Account Settings > Account Settings.
- On the Email tab, select the Exchange or Microsoft 365 account.
- Select Change.
- Under Offline Settings, move the mail-retention slider.
Typical choices include All, 12 months, 6 months, 3 months, and 1 month. Outlook 2016 also includes 3 days. Microsoft says the default for Exchange and Microsoft 365 accounts is normally 12 months.
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Cached messages are stored in an Offline Outlook Data (.ost) file. For example, with a three-month setting, messages older than three months remain on the server but are not synchronized into the local cache. Increasing the range uses more disk space and can make the initial synchronization take longer.
Add an account before trying to sync it
New Outlook for Windows
- Select View > View settings, or select File > Account info > Accounts > Your accounts > Add Account.
- Select a suggested provider, or enter the email address.
- Select Continue.
- Enter the password and select Done if prompted.
Classic Outlook for Windows
- Select File > Add Account.
- Enter the email address and select Connect.
- Enter the password if Outlook requests it.
- Select OK > Finish.
For a Hotmail.com or Live.com address, use the Outlook.com account type. Choosing Exchange or Microsoft 365 for these addresses can prevent existing messages and custom folders from appearing correctly.
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Set up IMAP or POP manually
Use manual setup when Outlook cannot identify the provider automatically or when the provider has supplied specific server, port, or SSL values. Microsoft generally recommends IMAP when manual server settings are required because it keeps mailbox folders synchronized with the server.
- In classic Outlook, select File > Add Account.
- Select Advanced options.
- Turn on Let me set up my account manually.
- Select Connect.
- Select IMAP or POP.
- Enter the incoming and outgoing server names, ports, encryption method, and authentication details supplied by the email provider.
- Select Next and complete the sign-in.
Gmail, Yahoo, iCloud, and other providers may require a setting to be enabled on their websites first. Some accounts, particularly certain IMAP and iCloud accounts, require an app password. Generate that password through the provider and enter it in Outlook instead of the normal account password.
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Sync Outlook on Mac
In supported Outlook for Mac editions, including Outlook for Microsoft 365 for Mac, Outlook 2024 for Mac, Outlook 2021 for Mac, and related Office editions, configure IMAP synchronization here:
- Select Outlook > Settings.
- Select Accounts.
- Select the IMAP account.
- Select Advanced.
Important options include:
- Sync all IMAP folders every x minutes controls the polling interval.
- Use IMAP IDLE (if the server supports it) keeps folders updated continuously and removes the need to run Send & Receive for that account.
- Download headers only saves message headers without downloading bodies and attachments until you open a message.
- Except in Inbox prevents the headers-only rule from applying to the Inbox.
- IMAP Root Folder can correct folder-display problems with providers that use a nonstandard IMAP folder structure.
For connection problems, make sure Outlook > Work Offline is not checked. Then open Tools > Accounts and verify the email address, username, password, SSL settings, ports, SMTP authentication, proxy settings, and server availability.
Sync Outlook email on a phone
If Outlook.com mail stops sending or receiving on one mobile device, remove that device’s mailbox partnership and add it again:
- Open Outlook.com in a browser.
- Go to Settings > General > Mobile devices.
- Select the affected device.
- Select Delete > Save.
- Power off the phone completely, then restart it.
- Open the Outlook mobile app and synchronize the mailbox again.
In the classic Outlook on the web interface, use Settings > Mail > General > Mobile Devices, select the phone, choose Remove, and select Yes.
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This removes the mailbox-device partnership; it does not wipe the phone. Also note that an account configured as IMAP or POP does not synchronize calendars or contacts in Outlook mobile. Those items require an Exchange ActiveSync account and the relevant calendar and contact permissions in the phone’s app settings.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Fix Outlook when email will not sync
Check whether Outlook is offline
In classic Outlook, Working Offline, Disconnected, or Trying to connect… on the status bar indicates that Outlook cannot reach the mail server. Select Send/Receive > Work Offline to return online. The button is shaded when offline.
If an Exchange or Microsoft 365 account does not show the Work Offline control, Cached Exchange Mode may be disabled. If the internet works but Outlook remains disconnected, the mail server may be unavailable. If webmail works while the desktop client does not, investigate local Outlook updates, cached data, or account settings.
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Repeated password prompts commonly result from a changed provider password, an expired corporate password, an incorrect username, or a case-sensitive password being entered incorrectly. The full email address is usually the correct username format, but some providers specify a different value.
Inspect the Outbox
A stuck message can hold up later messages. Open the oldest message in the Outbox first. An attachment larger than 20 MB is one documented cause. Remove or reduce the attachment, save the message, and try sending again.
Check mailbox storage
A full Microsoft cloud-storage allocation can stop both sending and receiving. Messages sent while the account is full are returned to the sender and cannot be recovered after the fact. Delete unnecessary mail and files, empty the relevant deleted-items folders, or increase the available storage.
Understand offline conflicts
Offline changes can produce unexpected results after reconnection. For example, if a message is deleted on the server while Outlook is offline and the cached copy is moved to another folder, Outlook may synchronize the cached copy back into that destination folder. Check both the original and destination folders when a supposedly deleted message reappears.
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Remove and re-add an account safely
Removing an account from Outlook does not delete the underlying email account. It removes the account from the app. In classic Outlook, locally cached content for that account is deleted from that computer; server-side mail remains available when the account is added again.
In new Outlook, a non-Microsoft account may offer Remove from only this device or Remove from all devices. Choose carefully, particularly on a shared Microsoft account or a device used by more than one person.
FAQ
What is the quickest way to sync Outlook?
In new Outlook for Windows or Outlook on the web, select Mail > View > Sync. In classic Outlook for Windows, select Send / Receive > Send/Receive All Folders. F9 is the keyboard shortcut in both cases.
Why is there no Send/Receive tab in Outlook?
You are probably using new Outlook for Windows. Microsoft replaced the former Send / Receive tab with the Sync command at Mail > View > Sync.
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New Outlook does not provide the same manual Sync capability for third-party accounts such as Gmail, Yahoo, iCloud, generic POP, and generic IMAP. Check the provider’s webmail service and account connection settings.
Why are old emails missing when I work offline?
Outlook may be saving only a limited period locally. New Outlook defaults to 30 days, while classic Outlook Cached Exchange Mode commonly defaults to 12 months. Increase the offline-retention setting if the computer has enough storage, or open older messages while online.
Does IMAP sync Outlook contacts and calendars?
Not in Outlook mobile. Microsoft states that IMAP and POP synchronize email but not calendars or contacts there. Exchange ActiveSync is required for those items.
Will removing a phone from Outlook erase the phone?
No. Removing a mobile partnership removes the mailbox-device connection. Restart the phone and synchronize the account again afterward.
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The Bottom Line
Use Mail > View > Sync in new Outlook or Outlook on the web, and Send / Receive > Send/Receive All Folders in classic Outlook. If synchronization still fails, check the online/offline state, account type, password, provider security requirements, Outbox, mailbox storage, and the amount of mail being kept in the local cache.
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