All doors lock automatically when the lock side is pressed. They unlock when the unlock side is pressed.
Driver's door

Front passenger's door

To lock all the doors from an open front door, press the lock side of the door lock switch and then close the door.
NOTE
When locking the doors this way, be careful not to leave the key inside the vehicle.
Locking, Unlocking with Transmitter
Auto Lock/Unlock FunctionMazda 6 Owners Manual: Locking, Unlocking with Door- Lock Knob
Operation from inside
To lock any door from the inside, press the door-lock knob.
To unlock, pull it outward. This does not operate the other door locks.
NOTE
The red indication can be seen when the door-lock knob is unlocked.
Operation from outside
To lock the rear and front passenger doo ...
Mazda 6 Owners Manual: Driving on Uneven Road
Your vehicle's suspension and underbody can be damaged if driven on rough/uneven
roads or over speed bumps at excessive speeds. Use care and reduce speed when traveling
on rough/uneven roads or over speed bumps.
Use care not to damage the vehicle's underbody, bumpers or muffler(s) when driving ...