and the most common option is to use a specific letterbox draught excluder. ‘This typically includes a brush or flap to seal ...

I didn't have a sofa, a dining table or a wardrobe, but before I even started looking at furniture, there was one £10 buy I bought almost as soon as I moved in: a letter box draught excluder.

All sorts of shops sell draught excluders, or you could even make one yourself by filling a large piece of fabric with old clothes or rice. Letterbox draught excluders are popular, as are letterbox ...