Office 365 (iOS 7) - Check Spelling and/or Grammar
This document explains how to check spelling and/or grammar using the iOS Mail Application.
Though iOS 7 doesn't check for grammatical mistakes, it can detect misspelled words and will underline the misspelled word with red dots.
Click on the misspelled word and the dictionary will present suggested words that closely match the misspelled word. When you choose one of the suggested words from the list, the suggested word will replace the highlighted misspelled word with your selection.