[{"id":1,"comments":[{"mail":"raj@gmail.com","Comment":"This product well worth the money"},{"mail":"janu@gmail.com","Comment":"Excellent Product"}]},{"id":2,"comments":[{"mail":"raj@gmail.com","Comment":"This product well worth the money"},{"mail":"janu@gmail.com","Comment":"Excellent Product"}]}]

db.collection.update({id:1},{$set:{"comments.$[comment].Comment":"New Comment",}},{arrayFilters:[{"comment.mail":"raj@gmail.com"}]})