0x85050042 Office 365 Sync Error on Mobile Data Fix

Error code 0x85050042 appears when the Outlook mobile app or the built-in Mail app fails to sync an Office 365 account over a cellular data connection. The fix is usually to adjust the app’s background data settings or toggle the connection type; this article explains the causes and step-by-step solutions.

What This Error Means

The 0x85050042 error is a synchronization failure code that Outlook for iOS and Android, and the Windows Mail app, display when they cannot reach the Office 365 server. The number itself is not a server-side problem; it is a client-side network error. In practice, it almost always means the device blocked the app’s access to mobile data, or the cellular network is interfering with the encrypted connection the app uses.

Users typically see this error when they are away from Wi-Fi and try to refresh their inbox. The email client may still show previously downloaded messages, but new mail, calendar updates, and folder changes fail to arrive. The error often resolves itself when the device reconnects to Wi-Fi, which is a strong clue that mobile data permissions or network settings are the root cause.

Why Mobile Data Triggers This Error

Office 365 sync uses HTTPS (port 443) to communicate with Microsoft servers. Most mobile networks allow this traffic without issue. However, three common factors cause the 0x85050042 code to appear specifically on cellular connections:

Background data restrictions: Android and iOS both have settings that prevent apps from using data when they are not in the foreground. If Outlook is restricted, the sync process is killed before it completes.
Data saver modes: Android’s Data Saver and iOS’s Low Data Mode can block background connections entirely, even when the app is open.
Carrier proxy or firewall: Some mobile carriers route traffic through a proxy that interferes with Microsoft’s authentication tokens, causing the sync to fail with a generic error code.

Less commonly, the device’s date and time being incorrect can break the TLS handshake, but that would usually affect Wi-Fi too. The fact that the error is mobile-data-specific points to the first two causes.

How to Fix It on Android

On Android, the fix involves granting Outlook unrestricted data access. The exact menu names vary by manufacturer (Samsung, Pixel, OnePlus, etc.), but the general path is:

Open Settings → Apps → Outlook (or the mail app you use).
Tap Mobile data & Wi-Fi (or Data usage).
Enable Background data and Unrestricted data usage if available.
Go to Settings → Network & internet → Data Saver and make sure it is off, or add Outlook to the Unrestricted apps list.
Force-stop the Outlook app, then reopen it and try to sync.

If the problem persists, check the carrier’s APN settings. Some networks require a specific APN for corporate email. You can find the correct APN by searching your carrier’s support page, but the default APN is usually correct for most users.

How to Fix It on iPhone and iPad

iOS handles background data differently. The key settings are:

Open Settings → Mobile Service (or Cellular).
Scroll down to the app list and make sure the toggle next to Outlook is green.
Go to Settings → Mobile Service → Mobile Data Options → Data Mode and select Allow More Data on 5G (or Standard if you are on LTE).
Turn off Low Data Mode in the same menu.
Open Settings → General → Background App Refresh and ensure Outlook is enabled.

After changing these, close Outlook completely (swipe it away from the app switcher) and reopen it. If the error persists, delete the account from Outlook and re-add it while on mobile data. This forces the app to authenticate fresh over the cellular connection.

What to Do If the Fixes Don’t Work

If you have verified all the above settings and the error still appears, the issue may be with the account itself or the network. Try these steps in order:

Toggle Airplane mode on and off to force the device to re-register with the cellular network.
Reset network settings on your phone (this clears saved Wi-Fi passwords, so be prepared to re-enter them).
Check if the error occurs on another device using the same mobile data SIM. If it does, the carrier’s network is blocking the connection; contact them.
Update Outlook to the latest version, as older builds have known sync bugs.
Remove and re-add the account – this often clears a corrupted sync token.

If none of these work, the problem may be on the server side. Microsoft’s service health dashboard (status.office.com) will show if there is an ongoing incident affecting mobile sync. In that case, wait for the service to recover.

Preventing the Error in the Future

Once you have fixed the immediate issue, you can reduce the chance of it recurring by:

Keeping Outlook’s background data permission set to Unrestricted if you regularly use mobile data.
Disabling Data Saver/Low Data Mode when you need reliable email sync.
Setting Outlook to sync automatically rather than manually, so it maintains a persistent connection.
Using the Outlook app instead of the default Mail app, as Outlook is better optimized for Office 365’s authentication protocol.

Also, note that some corporate IT policies enforce conditional access rules that block mobile data connections unless the device is enrolled in a management system. If your work account is affected, check with your IT department to see if there is a policy requiring a VPN or a specific network.

Frequently Asked Questions

Does this error mean my account is locked or hacked?

No. The 0x85050042 error is a network-level failure, not a security alert. Your account credentials are fine; the app simply cannot reach the server over the current connection. If your account were locked, you would see a different error asking you to sign in again.

Will using a VPN fix the error?

Sometimes yes. If your carrier’s network is blocking or interfering with Microsoft’s servers, a VPN can route the traffic through a different path. However, VPNs can also trigger corporate conditional access policies, so if you use a work account, check with IT first.

Why does it work on Wi-Fi but not on mobile data?

Because Wi-Fi and mobile data use different network paths. The app’s data permission settings are separate for each connection type on Android. On iOS, the Low Data Mode setting specifically targets cellular. The error is almost always caused by one of these settings being too restrictive.

Is this error specific to Outlook or does it affect other mail apps?

It can affect any mail app that uses Exchange ActiveSync or Microsoft’s modern authentication. The Windows Mail app and third-party clients like Nine or BlueMail can show similar errors. The fix is the same: ensure the app has unrestricted mobile data access.

Should I delete and re-add my account as a first step?

No. That should be a last resort because it can take time to re-download your mailbox. Start with the data permission settings, as they are the most common cause and take only a minute to check.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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