ResenderOnePlus: SMS forwarding stops in the background
Current OxygenOS is built on ColorOS and manages background apps the same way: an app that is not on screen is frozen unless you allow it to run. Two switches keep Resender forwarding with the screen off.
The two switches (OxygenOS 13 and later)
- Open Settings → Apps → Resender → Battery usage.
- Turn on “Allow background activity”.
- On some phones, also turn on “Allow auto launch” (Settings → Apps → Auto launch; on older versions Settings → Battery → App auto-launch).
- Allow background activity. Settings → Apps → Resender → Battery usage: allow background activity (also called Allow background running or Unrestricted, depending on the version). On OxygenOS 16 the same screen offers three choices instead of a switch — Allow background activity, Smart mode (Recommended), Restrict background activity: choose the first; on OxygenOS 15 the Optimize battery use line below switches to Don't optimize by itself once background activity is allowed.
- Allow auto launch. Settings → Apps → Auto launch on newer versions, Settings → Battery → App auto-launch or Settings → Apps → App management → Resender → Auto launch on older ones: switch Resender on, so the system starts it after a restart or when an SMS arrives while it is not running.
On OxygenOS 11 and earlier the screens differ: Settings → Battery → Battery optimization → Resender → Don't optimize, and Settings → Apps → Resender → Advanced for background activity. On every version, also take Resender off Android's own battery optimisation: the app's main screen has a button that opens the system list. OxygenOS 13 and newer also have a list of its own: Settings → Battery → Advanced settings → Optimize battery use — set Resender to Don't optimize there; the default is Always ask.
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, one of the switches is off — after a system update, check both again.
What no app can do
OxygenOS's battery screens 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 — the switches are yours. Skip them, and messages arrive late or not at all while the app has done everything it is allowed to do.
Questions
Forwarding is fine for a day and then messages come in bunches when I unlock the phone. Why?
OxygenOS freezes apps that are not on screen unless they are allowed background activity and auto-launch; the SMS reach Resender only when the system lets it run again, hence the bunches. Set the switches on this page once.
My OnePlus runs an older OxygenOS without these menus.
On OxygenOS 11 and earlier, go to Settings → Battery → Battery optimization, find Resender and choose Don't optimize, and check Settings → Apps → Resender → Advanced for an Allow background activity switch. The newer path on this page applies from OxygenOS 13.
Is the Android battery-optimisation switch also needed?
Yes, on every version. Resender's main screen has a button that opens the system list: find Resender and choose Don't optimize.
Why doesn't Resender switch these settings itself?
OxygenOS's 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, which a message forwarder is not.
Is this the same as OPPO?
Since OxygenOS 13 it is: the system is built on OPPO's ColorOS, so the switches are the same and only the names differ.