When is it appropriate to use a low-register tone in an email?

Using a low-register tone in an email is most appropriate when communicating with friends or family members. This tone is often more casual and relaxed, which aligns well with the informal nature of those relationships. Low-register language can help create a friendly atmosphere and foster open communication among people who share a personal connection.

In contrast, other contexts such as communicating with a superior, making a complaint, or writing to a colleague typically require a more formal or professional tone to convey respect, seriousness, or professionalism. Adapting the tone according to the relationship and context is crucial in effective email communication.