Quick wins for a faster PC:
Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →On current iOS, open Settings → Apps → Messages and turn off Send as Text Message. This stops the automatic retry that sends an undelivered iMessage through the carrier. It does not force every conversation to remain blue: messages to non-iPhone users, unregistered numbers, or non-iMessage conversations may still use RCS, SMS, or MMS.
Apple documents the setting and the red-exclamation behavior in its message troubleshooting guide.
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What changes when you turn off “Send as Text Message”?
With the toggle off, Messages will not silently switch an undelivered iMessage to SMS. If iMessage is unavailable, the message can remain unsent and display a red exclamation point or “Not Delivered.” You can retry iMessage, use another internet-based service, or deliberately choose the option to send it as a text message.
This is a choice between delivery-method control and automatic delivery reliability. A carrier message can create SMS/MMS records on your phone bill, depending on your carrier and account; Apple describes this in its Messages safety guidance.
Do not turn off iMessage
iMessage is Apple’s messaging service. Send as Text Message is only the fallback control. Turning off iMessage does not prevent fallback; it makes Messages use carrier messaging instead where supported. Leave iMessage on and disable only Send as Text Message if your goal is to stop automatic SMS fallback.
Why a green bubble can appear
Blue bubbles are iMessage. Green bubbles indicate another transport, but not necessarily SMS. On current iOS, green messages may use RCS, SMS, or MMS.
Rank #2
- The recipient uses a non-Apple phone.
- iMessage is disabled or has not activated on either device.
- The recipient is temporarily unreachable through Apple’s service.
- Your phone number is not selected in Send & Receive.
- The recipient recently changed phones or numbers.
- Your iPhone lacks Wi-Fi or cellular data.
- The conversation was created as a non-iMessage conversation.
Apple explains the differences between these message types at iMessage, RCS, and SMS/MMS.
Check that iMessage and your phone number are configured
- Open Settings.
- Tap Apps, then Messages.
- Confirm that iMessage is on.
- Tap Send & Receive.
- Under the addresses where iMessage can be received and replied to, select the correct phone number and Apple Account.
- Under Start New Conversations From, select your phone number if you want new chats to originate from it rather than your Apple Account email address.
The exact labels can vary by iOS release; older versions may show Settings → Messages without the Apps level. Apple’s setup instructions are available at this phone-number and email guide and this activation guide.
Fix messages that start from an email address
If Start New Conversations From is set to an email address, recipients may see that address and you may get separate threads from the same person. Change it to your phone number using Settings → Apps → Messages → Send & Receive. An existing thread may retain its original identity, so start a new conversation after changing the setting.
Use the right connection for the message type
| Message type | Connection needed |
|---|---|
| iMessage | Wi-Fi or cellular data |
| RCS or MMS | Wi-Fi or cellular data, subject to carrier and device support |
| SMS | Cellular network service; Wi-Fi Calling can support SMS over Wi-Fi in supported circumstances |
Wi-Fi access alone does not guarantee that SMS works, and cellular signal alone does not prove that your iMessage number is activated.
Rank #4
If iMessage is not activating
- Confirm that the iPhone has cellular service and can send SMS.
- Check Settings → Apps → Messages and turn on iMessage.
- Open Send & Receive and verify the phone number and Apple Account.
- Restart the iPhone and install available software updates.
- Ask your carrier whether SMS, including any international SMS needed for activation, is blocked.
- Allow up to 24 hours for carrier verification when Apple is activating the number.
Apple notes the SMS requirement and 24-hour estimate in its iMessage activation guidance. Repeatedly toggling iMessage is not a substitute for fixing carrier service, SIM status, or account registration.
iOS 26: check for a duplicate inactive SIM
Apple documents an iOS 26 issue in which an inactive physical SIM or eSIM has the same number as the active line. Symptoms include failed iMessage activation, green-only messages, messages originating from an email address, or the same number appearing twice in Settings → Apps → Messages → Send & Receive.
Apple’s remedies are to update to iOS 26.1 or later, or remove the inactive duplicate SIM/eSIM and then return to Send & Receive to activate the displayed number. See Apple’s iOS 26 guidance.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.If the recipient switched from iPhone to Android
A phone number can remain associated with iMessage for a while after its owner leaves iPhone, so other Apple devices may continue trying iMessage. Deregistration is primarily the former iPhone user’s fix, not a way to control fallback on your own iPhone.
On the old iPhone, go to Settings → Apps → Messages and turn off iMessage, then turn off FaceTime. If the phone is unavailable, use Apple’s online deregistration process. Apple says some devices may take several hours to recognize the change: deregister iMessage.
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Should you disable automatic fallback?
| Keep it on | Turn it off |
|---|---|
| Greater chance of automatic delivery when iMessage fails | No silent iMessage-to-SMS retry |
| Useful for urgent messages | Immediate visibility that iMessage delivery failed |
| May send a carrier message unexpectedly | You choose whether to retry or use another method |
| SMS/MMS records may appear with the carrier | A message can remain undelivered until iMessage returns |
Quick diagnosis
- Green from the start: the recipient or conversation may not be using iMessage; RCS, SMS, and MMS are all possible.
- Blue changes to green after a failure: automatic fallback is likely enabled; turn off Send as Text Message.
- Red exclamation after disabling fallback: iMessage is unavailable; check data connectivity, activation, and the recipient’s registration.
- Phone number missing or duplicated: inspect Send & Receive and your SIM/eSIM lines.
- Messages come from email: select the phone number under Start New Conversations From and begin a fresh thread.
Can you force every message to stay blue?
No. You cannot force iMessage for a recipient who does not use an Apple device, has iMessage turned off, has not activated the relevant number, is temporarily unreachable through iMessage, or is being contacted at an address that is not registered with the service. Disabling fallback only prevents this particular automatic SMS retry.
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