According to the manual, the two analog outputs are 12 bits (4096 steps) and can be programmed for -10 to +10, 0 to 10, -AOEXTRef to + AOEXTRef and 0 to + AOEXTRef.
If you program the 0 to 10V range, 10V/4096 steps = 2.44mV per step. So that's pretty close to your 2mV resolution.
I do not know about using AOEXTRef, it may give you finer resolution if you can apply a voltage less than 10V and still resolve it into 4096 steps (i.e. 5V/4096steps = 1.22mV resolution/step) Maybe someone else can cmine in on the use of the external reference. And then there is always the manual
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