Windows Live Mail auto-correct spelling and capitalization does not work.

I have checked the "auto-correct spelling and capitalization" box in the options menu, but in practice the program only capitalizes the personal pronoun "I," when typed in the lower case, and it does recognize misspelled words by showing the squiggly underscore.  It does not, however, auto-correct capitalization errors such as the beginning word of a sentence, which puzzles me.  I am hoping someone might tell me why.  Maybe I am doing something wrong.  Thanks for any help.