In Vermeer's, Delft is his city, universe the letter being received or written is usual and treated in a very direct way: letter received, some thoughts and answer.
"A Lady Writing a Letter", 1666, (left)
"The Love Letter"(right and detail)
There are more paintings with women receiving and writing letters and it is striking that there are no dramas and the expressions of the faces show control of emotions and no doubts about what to do with the envelop that has just arrived. In the left painting the woman is staring at the public and I can even listen: "Calm down, I know what to do and I'm so happy!" But this is me.