I assumed that that's how it works because I couldn't think of any other way to achieve the observed behavior, but pseudo roaming sounds plausible too, and presumably requires much less work on the carriers' side!
Would that approach also allow the extra functionality they seem to be offering, such as only recently messaged numbers and emergency contacts being able to send messages to satellite users, though? I suppose they could just reject all MT-Forward-SM with sender numbers they don't like?
> As far as I understand, that's how this kind of service usually gets implemented.
Do you have any other examples for solutions like this? Are you thinking of (pre-VoWifi) carrier apps or services that could receive texts, sometimes on multiple devices?
> Do you have any other examples for solutions like this
I have a vague recollection that Pebble had something like this to get texts on the Pebble watch.
> Would that approach also allow the extra functionality they seem to be offering, such as only recently messaged numbers and emergency contacts being able to send messages to satellite users, though?
Hmm, you could definitely do this with a "Stripe-like" approach, where the actual traffic goes over the usual protocols to ease implementation, but the carriers provide Apple an API to query messaging history in some way (which they probably already offer in their apps, and so have good integrations for anyway).
Stripe uses this pattern for fraud detection. Their card transactions still go over the antiquated ISO protocols from the 80's, because that's just what everybody integrates with and agrees on, but they can also speak a custom API directly with participating banks, mostly for better fraud detection and fraud-related information sharing.
Would that approach also allow the extra functionality they seem to be offering, such as only recently messaged numbers and emergency contacts being able to send messages to satellite users, though? I suppose they could just reject all MT-Forward-SM with sender numbers they don't like?
> As far as I understand, that's how this kind of service usually gets implemented.
Do you have any other examples for solutions like this? Are you thinking of (pre-VoWifi) carrier apps or services that could receive texts, sometimes on multiple devices?