Outlook does not sync: what you can do now

Outlook does not sync: what you can do now

Your Outlook does not synchronize as usual on your smartphone or computer? With our tips you can get the problems under control.

By Sven Wernicke

Outlook is actually a robust and sophisticated program for sending e-mails and managing appointments, contacts and calendar entries. But every now and then there are difficulties that primarily affect synchronization. Sometimes the calendar on the iPhone is not synchronized, other times folders are not displayed correctly. Fortunately, you usually only have to make small changes to make it "slip" again.

iPhone or Android smartphone does not sync with Outlook

If you are using the Outlook app for iOS or Android and the synchronization has already worked, repairing the affected mail account can already be the solution. And this is how it works:

1. Start the app as usual.
2. Switch to "E-Mail", tap on the "House" symbol in the upper left corner and select the gear wheel in the lower left corner.
3. Tap the email account that is having trouble.
4. Scroll down and tap "Reset Account".

When resetting the e-mail account, Outlook does not delete any content, but rather starts the account completely over with "factory settings". You may have to make adjustments afterwards. But that is done quickly and in the same place.

Calendar is not synchronized on the smartphone

Thank goodness there are digital calendars. But what use are they if, thanks to various problems with Outlook, you no longer know when friends are celebrating their birthday party? You should check the synchronization of the calendars on Android and iOS as follows:

1. Start the app as usual.
2. Switch to "Calendar" and tap the calendar symbol in the top left.
3. Select the calendars to be synchronized or displayed.

If the e-mail address with the connected calendar is not displayed, you have to delete the e-mail account and create a new one.

Tip: In the calendar selection, tap on the gear wheel in the lower left corner to access the e-mail account settings. There you can, depending on each individual account, switch the option "synchronize calendar" on or off. It is quite possible that the switch was deactivated here.

Important to know: Calendars can only be synchronized using Microsoft Exchange ActiveSync. If necessary, ask your email provider whether they support this standard. This function should be regularly active on a Microsoft Exchange Server.


Repairing the account often helps if there are synchronization problems. Image: © Microsoft 2018

Problems with the synchronization on Windows computers with Outlook

With almost all Outlook versions of the last few years – whether Outlook 2007, 2010, 2013, 2016, 2019 or Outlook from Office 365 – repairing e-mail accounts helps if there is a problem with synchronization. And this is how it works:

1. Start Outlook on Windows 10 or 11.
2. Select the "File" tab and "Account Settings".
3. Select the affected e-mail account and click on "Repair".
4. A window opens with information about the account. Click on "Next"
5. Follow the instructions.

Outlook may reveal here if a connection to the mail server is faulty or other inconsistencies have occurred. In the best case scenario, the repair will be successful and synchronization will resume as usual.

Similar to problems with the Outlook mobile app, the following also applies here: If that doesn't help, delete the email account in the same place and create a new one.

Problems syncing folders

Synchronization problems also occur with Outlook if the so-called OST or PST files are damaged. Then, for example, the folders for the inbox or the sent objects are defective. In this case, use Outlook's own tools.

OST files from Outlook 2003 and older can be repaired with the scanost.exe tool; newer Outlook versions are based on a PST folder structure. You can fix it with the scanpst.exe program. The programs are located in the standard folder of the Outlook installation, for example "C: Programs (x86) Microsoft OfficerootOffice16" for Outlook 2019.

In both cases you repair folder files like this:

1. Close Outlook.
2. Switch to your Outlook installation in the file manager.
3. Start scanpst.exe or scanost.exe.
4. Select the file to be repaired.
5. Follow the instructions until you finish.

After restarting Outlook, the folders should be displayed correctly again – including all their contents. A further explanation of what exactly the programs do is provided by Microsoft on a specially set up website .

If this does not work, but Outlook still starts, you can delete offline items in a folder and update them again:

1. Right click on the folder to be repaired and select "Properties".
2. Click on "Delete offline elements" and confirm this with OK.
3. Go to the "Send & Receive" tab and click "Update Folder".

Outlook should now download the previously deleted content again and synchronize it correctly.

More tips for solving sync problems

If none of that helps, try these tips:

1. On iOS or Android, close the Outlook app manually by closing it in the app switcher.
2. If resetting the e-mail account doesn't help, it can be worthwhile to delete the account in Outlook and create a new one.
3. Always helpful: Check whether you have the latest version of Outlook or update the app if an update is available.
4. As banal as it may sound: Sometimes restarting the smartphone helps to update the network settings and thus eliminate problems.


  • Whether on a mobile device with iOS and Android or on a computer with Windows 10/11: You should first try to repair your email account.
  • Calendars are only synchronized if they are selected and Microsoft Exchange ActiveSync is supported.
  • If the folder structure of Outlook is defective under Windows, Outlook's own tools can help.
  • Sometimes classic methods such as quitting and restarting Outlook or installing the update to the latest version are sufficient.

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