In a blender, combine the frozen mango, orange juice, tequila, Triple Sec and lime juice. Blend until puréed.
Add a splash of orange juice to a plate with edges.
Add the Tajín seasoning to a second plate with edges so that it coats the entire surface.
Dip the rims of the serving glasses in the orange juice then immediately in the Tajín.
Pour the margarita into the glasses and serve immediately.