Emails stuck in the outbox on an Android device are annoying, but the issue is rarely permanent, and solutions are available. The Gmail app outbox experiences this problem. Your emails show in the queue, but they do not push through and send. A stuck queue can happen with any email app, but Gmail is the default program on your Android device. Outlook and other programs may experience the same stuck-in-queue problems for the same reasons as the Gmail app.
Weak Signal Strength
Signal strength is a major factor when email is stuck in an outbox. You can write emails in your app, but they will not send without a strong connection. Even a moderate signal can cause emails to lag. If you are over the data limit on your plan, emails can stick for this reason as well. The provider may throttle down your speed, and your emails do not send. In this case, move to an area where your Android can access Wi-Fi, or send your mail from a laptop or desktop to push out the emails. In most cases, a draft saves at the least, and you can access, edit and send when you have a solid internet connection. If your emails are not sending through data, try connecting your phone to Wi-Fi and send again. If the problem persists, you either have a poor Wi-Fi signal or the app is not functioning properly.
Emails may stick in your queue when attached files are too large to send on your connection. Sending large files requires additional data and can cause the emails to process slowly in the outbox. Try sending without attachments, if possible. If the attachments are necessary, compressing the files may help the emails send even with a mediocre connection. They should send perfectly with a strong signal.
Email App Issue
Like any app, your Android email program can experience issues. Run any pending updates on your phone to attempt a fix. If this fails, do a soft reset by turning off the phone and turning it back on again. If your other apps are working properly, resetting the phone to factory settings should not be necessary. A full reset eliminates your saved passwords, photos and other data stored on the phone. As a last resort, uninstall the email app and reinstall the app. You will lose saved email passwords and need to re-enter your login information to access your email account on the newly reinstalled app. Try sending your emails again at this point.