How overdue is this for a tool YOU WILL USE every day? A quick download of Grammarly as a plug-in for your browser gives you the best proofreading system ever. It works on PC versions of MS Word and Outlook, not on Mac versions of MS Word as of yet. It's free, with an option to pay for more advanced critiquing of your writing available in the pay per month membership model.
I installed Grammarly as a plug-in for Chrome browser. I have a free account, so I can login from my PC at home or MacBook anywhere else. It quickly spell checks and analyzes the grammar validity of my musings. It checks for punctuation, wordiness, tense, use of colloquial phrases and more. It claims to learn your writing style, I haven't been on Grammarly long enough to see or benefit from any of this, but exciting if it's true.
Once on their system, you can type in Outlook, in your browser (Think long Facebook posts...) or cut and paste your writing into their window on their site for the corrective process to take effect. I do read many online articles each day, it's such a relief to know tools like this are available to assist those who don't write well and remain as a nice reminder of "the rules" if you are more involved with online publishing.
Have a look, let Grammarly surprise you with corrections and suggestions you wouldn't get from regular old Microsoft spell check. Wordpress postings, Twitter, whatever you do, Grammarly can help sharpen your message. At the very least, it will keep you clear of producing and sharing embarrassing grammar and spelling mistakes with the world!