Do not attempt this with a hairdryer and a multimeter. You need precision.
If you lack rework skills, consider eMMC to SDCard adapter. Desolder the faulty eMMC and solder a BGA-to-SD breakout board. Boot the POSTAL3 from a high-endurance SD card. You lose read speed (20MB/s vs 150MB/s), but thermal issues vanish. postal3 emmc hot
The keyword postal3 emmc hot is unique to this platform because of a known engineering flaw. On the Allwinner R16 reference design, the eMMC is connected directly to the PMIC (AXP223) without proper load switches. When the AXP223 fails, it sends 5V to the 3.3V eMMC rail. This doesn't instantly kill the chip but creates a "latch-up" condition in the eMMC's input buffers. Only heat can break the latch-up. Do not attempt this with a hairdryer and a multimeter
Other SoCs (like Rockchip RK3288 or Amlogic S905) have similar issues, but they are resolved by cold reflashing or JTAG. The Postal 3 requires heat due to the specific failure signature recorded in numerous repair forums (BadCaps, Reddit r/datarecovery, EEVblog). Desolder the faulty eMMC and solder a BGA-to-SD