A great email that you can receive about one time a week is called "ProofreadNOW". Just go to ProofreadNOW.com and register for free emails
It has a weekly challenge of usually 10 words with multiple-choice definitions, Weekly Grammar Tips (Example: anytime, sometime; on, up on, upon) and Word of the Week, with its pronunciation, Function (or sentence part, verb, noun etc), country of origin, date and finally definition.
Another is www.jansfreecontent.com, this site covers everything pertaining to grammar and spelling and proofreading.
Sorry about the soapbox. I am a retired teacher, daughter of two retired teachers. And sorry about the typing.
I just lost sight in one eye. Good news yesterday from Cincinnati Eye Institute, I have regained a tiny amount of sight and Dr. Golnik says there is no brain or nerve damage only bruising and since some sight has returned he is confident it will all return in time. Maybe weeks or months, but the good news is it WILL return! Praise God!!