If you wanted to argue that the postcard is the central image of Agha Shahid Ali’s poem, you could go to part two, where the speaker quotes a card “lying on the street.” The card starts off “We’re inside the fire, looking for the dark.”
Postcards, as well as letters, seem to represent or symbolize a message. That message is not a pleasant or peaceful one. The message is of violence and suffering.
People are “inside” a fire. They’re a part of a painful, harrowing situation. The postcard/letter theme might seem ironic or out of place. The people in the poem appear to need help right away. It doesn’t seem right that they’re bothering with postcards and letters.
Yet postcards and letters allow for communication and documentation. Perhaps that is what the speaker is trying to get across. They are trying to provide an account and bear witness to the atrocities in Kashmir.
The task seems to be futile. It seems hard to actually send his letters or postcards since each “post office is boarded up.” Even if the speaker could figure out a way to send them, they imply they’d be mailed to “doomed addresses.”
Yet perhaps there’s uncertainty with letters and postcards regardless of the situation. There’s always the possibility that a letter could get lost or that a postcard could be sent to the wrong address. There’s also the possibility that even if the letter or postcard are properly received, the person still might ignore them.
Perhaps that’s why the speaker of the poem is dedicated to sending out postcards/letters. They want to draw attention to their dismal situation. They want someone to take notice and perhaps respond or do something about it.