Spot–future parity
Future Price as of Today = Index Price as of Today + Risk Free Return (Treasury Bond Yield) - Expected Dividend until Expiry
Therefore, the 0.03% difference for June contract is (Treasury Bond Yield - Expected Dividend), which is negative, meaning that Expected Dividend > Treasury Bond Yield.
To determine by youself whether ES is overvalued/undervalued requires the knowledge of "unexpected changes to dividend", and for farther expiry, the "unexpected changes to treasury bond yield".
Because if you find ES overvalued, you can buy S&P 500 actual stocks on margin borowing (at treasury bond rate if you can) then short ES, and upon expiry you will have a profit.