If your free t is above 2.1% of total t your e2 WILL be too low.
If your free t is at 1-2% of total t and you feel good your estrogen WILL be just right.
If it is below 2% of total t AND you have high e symptons it WILL be too high.
There is no point testing e2 as a number is not useful. It is all about percentages and ratios between androgens and estrogen.