ResenderSamsung: SMS forwarding stops after a while
On a Galaxy phone, Resender usually works on day one and goes quiet on day three. That is One UI putting apps you have not opened for a while to sleep. Two settings, set once, keep it awake for good.
The two settings
- Open Settings → Apps → Resender → Battery.
- Choose “Unrestricted”.
- Done: the phone will not put Resender to sleep.
- Never sleeping apps. Settings → Battery → Background usage limits. Make sure Resender is in neither Sleeping apps nor Deep sleeping apps — remove it if it is — and add it to Never sleeping apps (Never auto sleeping apps on One UI 8). On older One UI versions the same screen is under Settings → Device care → Battery → App power management.
- Unrestricted battery use. Settings → Apps → Resender → Battery: choose Unrestricted. The default, Optimized, is what Android's own battery optimisation does, and the main screen of the app shows a red line until it is off.
The app has a button on its main screen that opens the right system list for the second step: find Resender there and choose Unrestricted, or switch battery optimisation off for it — whichever your version shows.
How to check it worked
Lock the phone, wait a minute, and send it an SMS from another phone. The email should arrive within seconds. If it arrives only after you unlock the phone or open the app, look at Background usage limits again: a system update sometimes puts an app back into Sleeping apps.
What no app can do
Samsung's sleep lists have no public interface. No app can read them, change them, or tell whether you have set them. Resender shows a red line when Android reports that it is being restricted and opens the right system screen for you — but the switch is yours. Skip it, and messages arrive late or not at all while the app has done everything it is allowed to do.
Questions
Forwarding worked for a day and then stopped. Why?
One UI watches which apps you open and after a few days moves the ones you don't into Sleeping apps, then Deep sleeping apps — and an app in deep sleep does not run in the background at all. Add Resender to Never sleeping apps and the list stops touching it.
What is the difference between Sleeping apps and Deep sleeping apps?
A sleeping app runs only occasionally in the background; a deep-sleeping app never does until you open it. Both delay an SMS forwarder; deep sleep stops it. Resender belongs in neither.
Do I need to turn off Adaptive battery?
No. Adaptive battery is fine as long as Resender is set to Unrestricted and sits in Never sleeping apps. Those two settings exempt it from what Adaptive battery does to other apps.
Why doesn't Resender just set this itself?
Samsung's battery screens have no public interface: no app can read or change them. The one Android setting an app could change with a single dialog needs a permission Google Play grants only to alarms, calling and similar categories — a message forwarder is not one of them.
Which Samsung phones does this apply to?
Every Galaxy phone on One UI 2 or later: Galaxy S, A, M, Z and Note series. The menu wording moves a little between One UI versions, but Background usage limits and Never sleeping apps exist on all of them.