utmost: at the highest point 
upmost: in the highest position 

Although the wording in the definitions of the two words differ, the words themselves have the exact same meaning. 

I propose that the English language eliminate the redundancy found among these two words and deprecate the word "utmost". The English language, like any, needs to have controls in place to allow for evolutionary change. All computer languages I know of make use of versioning to allow for enhancements. I believe our human languages should be no different.  It is by this rational that I can conclude that the english language, in a word, sucks.