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You’ll see a little red alert exclamation point appear to the right of the message (this will usually only happen if you’re in an area with really bad cell reception). To have it try to resend the text message, just tap on the exclamation point icon, then tap the Try Again button. If it’s successful, the message will appear in a bubble just like always and the exclamation point icon will be gone. Otherwise, it will stay there in the bubble with the red warning beside it. Also, if you tap the Send button, and then switch to another app (thinking your message was sent with no problem), the Messages app will try to alert you that the message didn’t go by adding a red exclamation point warning to the Messages app’s icon (as shown above right).