This study sought to explore the formality styles of writing among intermediate EFL Iranian learners to scrutinize their competence in the writing skill. A convenience sample of 30 students were chosen through Oxford Quick Placement Test (2001) from among 60 university students. The first group sent their messages (essay tasks) through e-mail and the second group used Telegram. A corpus containing a total of 240 written texts was extracted from both groups. This corpus was then analyzed and compared in terms of formality styles. A detailed comparison of the two sub-corpora revealed a significant difference between texts written and sent by Telegram application and e-mails. The results of data analysis also indicated that informality and formality markers potentially function as distinctive factors, capable of differentiating between the texts sent by Telegram and e-mails. Ultimately, the essays sent by Telegram (containing 5 factors including contractions, questions, modal verbs, opening sentences, vocabulary) were recognized to use more informal styles of writing than emails. Taking the current study’s findings into account, academic writing pedagogy may benefit from a focus on employing appropriate writing strategies and techniques to accelerate Iranian university students’ writing development.