What is the correct way to spell a words like email, ecommerce, etc. ?

To be strictly ‘correct’, these e words should be written with a hypen: e-mail, e-commerce, since e is short for electronic. The hyphen may disappear over time, since that is what midword hyphen tend to do. The Oxford English Dictionary gives the preferred form as one word email for the noun form, but e-mail for the verb form although many dictionaries prefer E-mail.