I am looking through a Postcard from WWI and it says "Write to Bank of Montreal 24 Cockspur St Trafalgar Square London and they will forward it."

What does that mean exactly? I was thinking that banks may have sent and received packages, but wouldn't they have mail for that? Other than that, would people casually send money overseas to people back home? I'm certain its not money because he is writing to his friend or co-worker it seems.