This essay examines the mail art of artist duo Polvo de Gallina Negra (Maris Bustamante and Mónica Mayer, 1983–93) and artist Magali Lara in 1980s Mexico. It analyzes two specific cases: Polvo de Gallina Negra’s project Carta a mi madre (1987) and a postage stamp by Lara (c. 1980) to argue that both used the possibilities of mail art as a mode of feminist disruption through approaches of play, invention, and surprise, ultimately working to subvert the patriarchal structures that oppress women. However, despite their innovative practices, these female figures continue to receive less attention in art historical scholarship of Mexican mail art and Latin American mail art overall. Furthermore, most scholarship on mail art in Mexico characterizes the conceptual practice as investigations of state surveillance or exercises of freedom under the Partido Revolucionario Institucional. Rather than taking this approach, I suggest that the work in this study looks toward more specific systemic structures that oppressed women under the auspices of modernity. In this sense, while the more recognized Mexican mail artist Ulises Carrión described the target of his mail as “The Big Monster,” we can see how the subversion tactics of Polvo de Gallina Negra and Lara are directed at a similar yet distinct monster: patriarchal control and possession in its multiple, cross-historical, national, and transnational manifestations.