“Message not sent. Check network” (Mobile)

The "Message not sent. Check network" error occurs on the Gmail mobile app for Android and iOS when an outbound email fails to upload to Google’s mail servers. The unsent email drops into the local Outbox folder, accompanied by an alert banner indicating a network failure. This error frequently appears even when your mobile device has an active Wi-Fi or cellular internet connection. The problem is typically caused by background sync restrictions, a blocked or oversized attachment in the Outbox queue, an expired authentication token, or mobile VPN interference.

How to Fix “Message Not Sent. Check Network” on Mobile

To resolve the “Message not sent. Check network” mobile error, open the Outbox folder in the Gmail app, locate the stuck message, and verify that its attachment does not exceed mobile limits. Next, toggle Airplane mode on and off to reset the data connection. If the message remains queued, clear the Gmail app cache in your device settings, disable any active VPNs or battery savers, and resync the account.

Diagnostic Flowchart

"Message not sent. Check network" Error
                     │
                     ▼
          Check Outbox in Gmail App
                     │
    ┌────────────────┴────────────────┐
    ▼                                 ▼
Stuck Message with Large File    Text-Only Message Stuck
    │                                 │
    ▼                                 ▼
Exceeds cellular upload limits    Background Sync / Auth Failure
  • Save text to draft              • Check Battery Optimization
  • Delete message from Outbox      • Toggle Airplane Mode / VPN
  • Re-upload via Wi-Fi             • Clear Gmail App Storage Cache

Step 1: Clear the Outbox Queue

When a single email fails to send from the mobile app, it gets stuck in the Outbox folder (not the Sent or Drafts folder). Once a message is stuck in the Outbox, it blocks all subsequent outgoing emails behind it, causing them to fail with the same generic network warning.

1. Open the Gmail app.
2. Tap the menu icon (three horizontal lines) in the top-left corner.
3. Scroll down and tap Outbox. (If the Outbox folder is missing from the list, no messages are currently queued).
4. Inspect the stuck email:
   • Does it contain a large video, high-resolution photo, or PDF attachment?
   • Cellular networks often time out when uploading files larger than 10 MB over unstable connections. For more details on attachment limits, see Troubleshooting “Message too large” (Inbound/Outbound).
5. Tap and hold the stuck message, copy any important text, and delete the message from the Outbox.
6. Return to your primary Inbox and send a simple, text-only test message to confirm the queue is unblocked.

Step 2: Eliminate Network and Proxy Interferences

Mobile operating systems often drop long-running SMTP/API upload sockets if the network changes while the message is sending (such as walking out of Wi-Fi range onto mobile data).

1. Cycle Radio Interfaces: Turn on Airplane Mode for 10 seconds, then turn it off. This forces the device baseband to re-establish clean DNS routing and IP leases.
2. Disable Active VPNs and Private Relays:
   • On iOS, go to Settings > General > VPN & Device Management and disconnect third-party VPNs. If using iCloud Private Relay, temporarily toggle it off under Settings > [Your Name] > iCloud > Private Relay.
   • On Android, disconnect apps like Cloudflare WARP, Google One VPN, or ad-blocking DNS profiles (e.g., NextDNS/AdGuard) that intercept port 443 and 587 traffic.
3. Check Captive Portals: If connected to public Wi-Fi (such as hotel, airport, or coffee shop networks), open your web browser and accept the login terms. The Gmail app cannot transmit data if the connection is trapped behind a captive splash screen.

Step 3: Remove Background Sync and Battery Restrictions

Both Android and iOS aggressively throttle background network activity to extend battery life. If Gmail is marked as battery-optimized, the OS will terminate its connection mid-transmission whenever the screen turns off.

On Android:

1. Open device Settings > Apps > Gmail.
2. Tap Mobile data & Wi-Fi.
3. Enable Background data and turn on Unrestricted data usage.
4. Go back one screen and tap App battery usage (or Battery).
5. Change the setting from “Optimized” to Unrestricted.

On iOS (iPhone/iPad):

1. Open iOS Settings.
2. Scroll down and tap Gmail.
3. Toggle the Background App Refresh switch to ON.
4. Tap Cellular Data and ensure it is enabled.
5. If Low Power Mode is active (yellow battery icon), turn it off under Settings > Battery. Low Power Mode pauses background email sync automatically.

Step 4: Clear Application Cache and Data (Android)

Corrupted local databases or temporary files can break the sync connection between the mobile app and Google’s servers.

1. Open Android Settings > Apps > Gmail.
2. Tap Storage & cache.
3. Tap Clear cache.
4. Force close the Gmail app and reopen it to test delivery.
5. If the error continues, return to the storage menu and tap Clear storage (or Clear data). This deletes local application cache files, but it does not delete your emails, which remain safe on Google’s cloud servers.
6. Reopen Gmail and allow your folders to resynchronize over a stable connection.

If sync remains stalled across all Google services, your device may be experiencing broader connection issues. See Fix: “Connection to server failed” (Gmail Android).

Step 5: Refresh Authentication and Security Tokens

The mobile app will display a network error if your account session has expired or if your Google Workspace administrator applied a security challenge that the app cannot process in the background.

1. Look in your phone’s notification shade for an alert stating Account action required. If present, follow the instructions in Fix: “Account Action Required” notification on Android.
2. If using a corporate Workspace account, ensure your device complies with your organization’s security policy. If your device lacks an active PIN or biometric lock, the security profile may block outbound traffic.
3. If no alert appears, manually remove and re-add the Google account:
   • On Android: Go to Settings > Passwords & accounts, tap your Google account, and tap Remove account. Then restart your phone and sign back in.
   • On iOS: Open the Gmail app, tap your profile icon in the top right, tap Manage accounts on this device, select Remove from this device, and sign back in.

Step 6: Verify Daily Sending Quotas

If your account recently sent a large volume of messages, your account may be temporarily blocked from sending. Google enforces strict recipient and rate limits across both web and mobile clients:

• Standard paid accounts are capped at 2,000 daily recipients, while free consumer accounts and trial licenses are restricted to 500 recipients per rolling 24 hours.
• If you have exceeded this quota, mobile sends will fail until the rolling cooldown period expires.

To determine if your account is locked due to sending volume, check your account against the limits outlined in Fix: “550 5.4.5” Daily Sending Limit Exceeded and the Guide to Workspace Sending Limits by License.