Hello Pemi,
Video is the present and future of content marketing, and people generally gravitate towards video, so it is a really effective way to reach your audience, but you mustn't ignore other content formats that may be more useful in getting a particular message across. Yes, email is still very efficient and has a very high Return On Investment (ROI). Some of the most common mistakes are not understanding your audience, not giving your strategies/plans enough time to give the desired results, not evolving and being so afraid of failing you take no chances.