iPhone 7+ Can Not Send SMS without SIM

David Kelly1 wrote:

My iPhone 11 has enabled "Text Message Forwarding" to 5 devices: (2) Macs, (1) iPad, an iPhone SE and an iPhone 7+. Both iPhones lack SIMs. Both receive incoming phone calls when the 11 is near. All send and receive texts with others on iMessage. The Macs and iPad can send/receive SMS texts which are not iMessage. Today's problem is the SE and 7+ cannot send an SMS message the way the iPad can, yet they receive SMS.

Comparing settings in General, Messages, and iCloud, I can't spot a difference between the iPhones and iPad. SMS is enabled but I don't have a SIM in the devices for it to use SMS directly. Disabling SMS makes no difference. And pretty sure last year the SE could send SMS to non-iMessage users, but not now. All iOS devices are 13.3. Reset of network settings (which rebooted the phone and lost WiFi settings but not Bluetooth) didn't change anything.

The difference is the SIM. The phone's can't send an SMS without a SIM. They are recieving them because they are being forwarded by a phone that can.

I don't recall any phone every being able to send an SMS without a SIM, even with Continuity.

Macs and iPads (doesn't matter whether they have a SIM or not) work differently. All the SMS features are handled through the iPhone. You'll see the difference in iMessage/Facetime activation. Phones need to be able to send an international SMS. iPads and Macs don't.