Phone Battery Optimisation Is Killing Your Email Sync

The email arrives hours late — not when it was sent, but the moment you unlock your phone and open the app. The subject line says urgent. The message reached its destination on time; your phone decided to defer it.

Battery optimisation is the umbrella term for system features that suspend background apps to extend screen-on time. Android's built-in implementation is called Doze mode, first introduced in Android 6. Apple implements the equivalent through Background App Refresh. Every major manufacturer — Samsung, Xiaomi, OPPO, Vivo, OnePlus, Huawei — then adds a second enforcement layer on top, with its own setting names, its own defaults, and its own location in the menu tree. The combined result is the most common cause of phone battery optimization stopping email notifications.

The fix is to exempt your email app from those restrictions. The exact setting name and where to find it changes with every phone brand, which is why this specific problem accounts for so many support threads. This guide covers stock Android, the five most widely deployed manufacturer skins, and iOS in one place.

Before You Change Anything#

Two things are worth settling before you touch battery settings.

Push versus pull. Not all email accounts deliver messages in real time. Standard IMAP accounts — most self-hosted inboxes and many business mail servers — are configured to poll on a schedule rather than wait for the server to push. If your app fetches every 15 minutes by default, exempting it from battery optimisation will not make messages arrive any faster than that interval. Check your mail app's account settings for a sync frequency or fetch option. If real-time delivery matters, you may also need a push-capable account setup.

Battery impact. Setting an app to unrestricted background access means it can wake up and connect to the network at any time your screen is off. For a mail client this cost is small — periodic network checks account for a fraction of a percent of battery per hour. But on a device with a degraded battery that struggles through a full day, even small additions are meaningful. Know the tradeoff before you change the setting.

How to Exempt an Email App from Battery Optimisation on Android#

These steps work on Google Pixel phones and Android One devices. If your phone is made by Samsung, Xiaomi, OPPO, Vivo, or Huawei, follow these first and then check the manufacturer table below — those brands add a separate enforcement layer that this stock exemption does not reach on its own.

1. 1

   Open Settings and tap Battery

   On some devices this appears as Battery and Power. If you cannot find it immediately, use the Settings search bar and type Battery.

2. 2

   Tap Battery Optimization or App Battery Management

   The exact label varies by Android version, but the option lives somewhere in the Battery menu. Look for a subheading that mentions optimization or app management.

3. 3

   Switch the list view to All apps

   Use the dropdown or filter — often labelled Not optimized — to show every installed app rather than the short default list.

4. 4

   Find your email app and tap it

   Scroll or search until you find the app. Tap it to reveal the restriction options.

5. 5

   Select Unrestricted and confirm

   Some Android versions label this option No restrictions instead. Tap Done or Apply if a confirmation appears.

iPhone and iPad: Background App Refresh#

On iOS the equivalent control is Background App Refresh. Apple manages background processes at the system level, so there is no per-manufacturer variation — but there is a two-level toggle structure that catches a lot of people out.

The global switch must be on before the per-app setting does anything at all. If the top-level toggle is Off, no app can refresh in the background regardless of what its individual setting shows. Always check the top level first.

1. 1

   Open Settings and tap General

   General appears near the top of the main Settings list, below your Apple Account row.

2. 2

   Tap Background App Refresh

   The first control on this screen is the global toggle. Confirm it is set to Wi-Fi or to Wi-Fi and Mobile Data, not Off.

3. 3

   Scroll to your email app and enable its individual toggle

   Each app has its own switch below the global setting. Turn on the toggle for your mail app.

Why the Setting Looks Different on Every Phone#

Stock Android provides a battery exemption API that any manufacturer can implement, but each one wraps it in different terminology, places it in a different menu path, and often supplements it with additional enforcement the stock API does not expose. Menu locations also shift between major OS versions. The table below maps the most common platforms. If a path does not match your device, the dontkillmyapp.com database maintains per-model guides with annotated screenshots contributed by users of that specific hardware.

What to Do When the Fix Does Not Work#

Clearing the battery exemption removes the most common blocker, but it is not the only one. If mail is still delayed after you set unrestricted access, work through the following in order.

• Notification permission: Android 13 and later require apps to request explicit notification permission. Go to Settings, then Apps, tap your email app, then Notifications, and confirm that notifications are allowed. This permission is separate from battery optimisation and must be granted independently.
• A second sleep list: Samsung, Xiaomi, and OPPO maintain a device-level sleeping or auto-start restriction list that runs independently of the per-app battery exemption. See the extra step column in the table above for the specific location on each brand.
• Polling interval: If your account uses IMAP without push support, there is no faster delivery signal than the fetch interval allows. Shorten it in the app's account settings, or check with your mail provider whether push is available.
• Data Saver: Android's Data Saver mode blocks background network access for all apps except those you explicitly permit, overriding the battery exemption. Check Settings, then Network and Internet, then Data Saver.
• Expired authentication: An expired OAuth token or a changed password silences an account entirely until you re-authenticate. A persistent account warning banner in the app usually signals this.
• Force-stopped state: If you swiped the app off the Recents screen while battery optimisation was active, some manufacturer skins move it to a force-stopped state. Open the app once manually to re-register it for background wake events.

A Faster Way: Server-Side Sync#

The exemptions above work, and they are the right fix for the phone you already have. What they are working around is a structural issue: a client app has to wake up to check for mail, and the operating system is designed to stop apps from waking up.

Server-side sync inverts that order. New messages arrive at the server first, and the server pushes a notification to your device over a persistent, lightweight channel — the same delivery path that app notification services use. On Android, this uses the high-priority message path that bypasses Doze mode deferral. On iOS, Apple Push Notification service delivers the notification independently of Background App Refresh: Background App Refresh governs whether an app can self-wake to fetch data, not whether a server can push to it.

We build AI Emaily, an AI-native email client that syncs on the server rather than the device. Notifications reach your phone through this push path without requiring the app to be awake beforehand, and Gmail, Outlook, and IMAP accounts appear in one unified inbox. There is a native iOS app; on Android, AI Emaily is a PWA that installs to your home screen and receives push. If you are still seeing gaps after working through the manufacturer exemptions, the architecture difference those exemptions are compensating for is what AI Emaily sidesteps by design.