Your iPhone's Messages app supports both Apple's free iMessage service and standard SMS text messaging. The free iMessage service provides a convenient way to send individual and group messages on various Apple devices without needing to pay for regular text messages. The colored speech bubble you see used with a message does not indicate the message status on the recipient's end but rather indicate how the message was sent – as a regular SMS text message or an iMessage. Your sent iMessages always appear in a blue speech bubble. Although you cannot determine precisely when your contact receives or reads your message unless that person has turned on the read receipts option, you can rest assured that Apple stores your message until your contact is back online and then delivers to your recipient's iPhone or other Apple device.
Identifying Message Bubble Colors
The blue speech bubble on an iMessage indicates you are sending secure encrypted messages that go from your Apple device to another Apple device with the Apple Messages app and iMessage service. If the message you send is addressed to someone without the Messages app, it transmits via regular SMS text messaging, and the sent messages appear in a green speech bubble. The green color indicates these messages are traditional SMS or MMS messages delivered to a phone. Both iMessages and regular texts you receive from others always have gray bubbles; this is the same whether you are chatting with a group or just one person.
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Detecting iMessage Delivery
When you send an iMessage, the word "Delivered" usually appears immediately under the blue speech bubble, which indicates the message has arrived at Apple's servers, not that your recipient has seen it. Apple temporarily holds the message until the iPhone comes online and then delivers it to the recipient.
If you receive an error message when you send an iMessage, it usually indicates that the problem is with the recipient's address or phone number. Confirm the accuracy and try again. If you see a red "Not Delivered, try again?" message under the speech bubble, try again. This message has not reached Apple's servers.
Will iMessages Deliver to a Dead Phone?
When the recipient's phone is turned off or dead, Apple holds the iMessages sent to that account on its servers and delivers them to the iPhone when the recipient turns it back on. However, this does not mean your contact won't be able to read your message if the phone is dead. If the recipient activated "Text Message Forwarding" in the iPhone's settings, the iMessages are also sent to your other Apple devices signed in to your account, such as an iPad, iPod Touch or Mac with the Messages app. The message is delivered to any of these devices when it is active, even if the message has not reached the phone.
Confirming Message Receipt
For you to know that a person has read your iMessage, that person must have turned on "Send Read Receipts" in the Messages settings. This option is not enabled by default, and it is not available for group chats. If your contact enabled the feature, then you'll see the word "Read" below the message you sent along with a timestamp indicating when the message was seen.