The first thing to do is to ensure that your device is connected to a stable Wi-Fi. Inspect the connection and see whether any other app suffers from network issues. If the problem is isolated to Outlook, then you can move to another step.
On the other hand, if you have connectivity issues in general, try these steps:
Reboot your phone/tablet and your wireless router.
Enable Airplane mode for a couple of minutes. Disable it, connect to a network, and try syncing emails again.
Reset Network Settings.
Solution 2 – Reset the account
The Outlook app offers a built-in reset option if emails are not syncing. You can find it in the individual account settings within the app. Once you reset the account, it will restart the syncing process and, hopefully, fix the problem for good.
Follow these steps to reset Outlook account:
Tap on the hamburger menu and then on the cog-like Settings icon.
Open the Microsoft account that won’t sync.
4. Scroll down and tap Reset Account.
Solution 3 – Remove and add the account again
Moving forward. Of course, in case you still couldn’t resolve the sync issue, you can try and remove the account. Along with that, you can navigate to Outlook in a web browser and remove the Android device from the Sync list.
In order to do so, follow the steps from the previous solution just, instead of Reset, tap Delete Account. Add the account again afterward and look for improvements.
Solution 4 – Reinstall Outlook
If the previous steps weren’t of any help, let’s reinstall the app and give it another go. Usually, Microsoft tends to its Play Store apps but there might be a bug at the current version. If that’s indeed the case, the reinstallation should fix it for good.
Follow these steps to reinstall Outlook on Android:
Open the Play Store.
Search for Outlook and expand the Microsoft Outlook: Organize Your Email & Calendar app.
Tap Uninstall and restart your device.
Now, open any browser, navigate here, and sign in with the affected Outlook/Hotmail account.
Under the Mobile device in the left pane, locate your device, highlight it and click on the minus sign (-) to delete it.
After that, just install Outlook again, add your account, and look for improvements.
Solution 5 – Download an older APK version of Outlook
Finally, if you are still stuck with Outlook not syncing, you can roll back the app by installing an APK from APK Mirror (or any other APK aggregate of your choice). There’s definitely something flawed with the current version so, by installing an older version, Outlook should be able to sync emails successfully.
Here’s how to download and install an Outlook APK on your phone or tablet:
Uninstall Microsoft Outlook as explained above.
Navigate to APK Mirror, here, or any other APK hub online.
Download an older APK version but not older than two months.
Grant permission to install apps from untrusted sources.