Xiaomi
Turn MMS Read Receipts On or Off auf Xiaomi
MMS read receipts tell a sender whether you opened their message, separately from the delivery confirmation used for plain SMS. On Xiaomi phones running MIUI, this option lives inside the Messages app rather than the general system settings, which is why many users cannot find it under Settings alone.
To check or change the current state, open Tap on Messages ➔ Open the Menu ➔ Tap on Settings ➔ Tap on General ➔ Tap on Chat features ➔ Enable or disable Send read receipts. Turning this on sends an automatic notification back to the sender once you open their MMS. Turning it off stops that notification, but it also means you will not receive read confirmations for MMS messages you send yourself, since the feature works both ways.
Dual SIM behavior
If your device runs two SIM cards, MIUI treats each line as an independent messaging profile. That means the Send read receipts toggle can be active on one SIM and disabled on the other, so check the setting again after switching your default messaging SIM.
This option only affects MMS group and media messages, not regular SMS delivery reports, which are controlled by a separate toggle in the same Chat features menu.