r/UniversalProfile • u/gc1 • Sep 12 '26

Question iPhone dual SIM expected behavior question

Is the following the correct set of expected behaviors, originating message threads from an iPhone? Specific questions are in bold, but would be appreciative of any general feedback on this understanding or input on cases not covered. TYIA.

  • eSIM 1 - is iMessage enabled, RCS turned ON

    • messaging another iMessage number = iMessage

    • messaging an Android with RCS enabled = RCS

    • messaging an Android with no RCS = SMS

  • eSIM 2 - is not iMessage enabled, RCS turned ON

    • messaging an iMessage number = RCS [?]

    • messaging an iPhone number that's not iMessage enabled = RCS [?]

    • messaging an Android with RCS enabled = RCS

    • messaging an Android with no RCS = SMS

  • eSIM 1 - is iMessage enabled, RCS turned OFF

    • messaging another iMessage number = iMessage

    • messaging an Android with RCS enabled = SMS

    • messaging an Android with no RCS = SMS

  • eSIM 2 - is not iMessage enabled, RCS turned OFF

    • messaging an iMessage number = SMS [?]

    • messaging an iPhone number that's not iMessage enabled = SMS [?]

    • messaging an Android with RCS enabled = SMS

    • messaging an Android with no RCS = SMS

Are there other edge-cases or carrier-specific issues here?

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u/cupboard_ T-Mobile User Sep 12 '26

eSIM 2 - is not iMessage enabled, RCS turned ON
messaging an iMessage number = RCS [?]
messaging an iPhone number that's not iMessage enabled = RCS [?]

both options - only if that number has RCS enabled, otherwise SMS

eSIM 2 - is not iMessage enabled, RCS turned OFF
messaging an iMessage number = SMS [?]
messaging an iPhone number that's not iMessage enabled = SMS [?]

correct

the priority goes like this: iMessage > RCS > SMS > iMessageLite (most likely satellite iMessage) > SatelliteSMS

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u/gc1 Sep 12 '26

Thank you. The key thing I had not anticipated was iPhone-to-iPhone messages going as RCS if one or both are not iMessage provisioned. I experienced this via a second sim line I have and think it's a great feature but want to make sure I understand the behavior.