How do I create a useful learning objective?
Disclaimer: Mostly opinions.

First. I'd suggest perhaps one level down in terms of the verb choice. What the course will likely do is to introduce an array of possible mistakes in these activities so that audience can avoid committing them. So, the objectives should not be "avoiding" but rather along the line of "familiarize with", "able to list", or "be introduced to a survey of." Whether to avoid or not is really not the takeaway.

The general tip of writing objectives is to think: "If I am going to assess whether my audiences have learned my messages, what are the aspects I will be testing?" Very likely, you are not going to give them a mistake-prone situation and see if they avoid it in real life; but perhaps provide a list of scenarios and see if they can identify which one is likely going to cause a mistake, and which is a safer/more professional approach. In other words, you'll be testing their knowledge and attitude, and not their behavior after class. Yet. your current objectives are about their behaviors.

Second, perhaps add some specificity. E-mail for what? Talking to family members? Someone whose pets just died? Business? Potential dates? If someone just picked up this one page of objectives, is there enough information for the person to decide if he/she should consider your course offer?

Third, consider providing a clear set of general benefits. After learning all these objectives, what will likely happen? Will they have a better commands in communicating with people in professional setting? In other words, what are the aspirations of your course, that you won't be teaching directly, but the audience may be able to realize that if they follow your advice?

Meanwhile, beware of over-promising. Communication is at least a two-way process and even your audience did everything "right," mistake may still happen. I'd suggest perhaps more neutral wording such as "achieve high level of clarity..." so as to "minimize potential miscommunication or mistakes."