Email etiquette is an important skill, especially in professional settings. Research demonstrates that undergraduate students follow email rules when given written instructions plus an example. The purpose of the present study was to evaluate the effects of computer-based email instruction on undergraduate students' email etiquette and to assess the social validity of that instruction. The email instruction package was delivered through an online learning management system and consisted of written instructions plus a model, a quiz, and quiz feedback. We measured email etiquette by scoring emails from course assignments using a checklist. The instruction package produced a replicated increase in mean email checklist scores across two sections of introductory psychology, and checklist scores were elevated when participants sent emails in a novel context. The results of the social-validity assessments suggest that the goals were important, the procedures were acceptable, and there were meaningful improvements in email etiquette for some participants.