Gmail stuck in the Outbox on Android? Try a plain email

In the Gmail app, check the selected account, then look in Outbox and Sent. Keep a copy of the message text and any files before removing or rewriting anything. Test with a short subject you can recognize. Look for the test in Sent and check whether it arrives in your inbox. Before sending the original again, check Sent for it so you do not send a duplicate.

Try a stable connection and let the upload finish. If it still fails, open the original if it is editable, or start a new message from your saved copy. Reattach a smaller file or add a Google Drive link, then check that the intended recipient has access. Use restricted sharing for private files. Check the original queue entry before resending.

Use the same account to compare a plain message at mail.google.com in a browser. If it sends there, pull down from the top of the Gmail inbox to refresh. Then go to Gmail → Menu → Settings → your account and check Sync Gmail under Data usage. Update the Gmail app and restart the phone if needed. Clearing app storage is a last resort because it can erase drafts and settings. Save any unsent work first.

Check the error in the browser and check Google Account storage. A full account blocks both sending and receiving. If a work or school account displays a policy error, ask your administrator about the message. If the original already appears in Sent but the recipient cannot find it, check the address and look for a delivery error. That is a different problem from a message still waiting in Outbox.