We have the same problem with Daisy.
She goes nuts when she hears the postman, or someone putting junkmail through the door.
She scrabbles on the laminate, then leaps for the door.
We wasted money on one of those 'catch the post' baskets.
This merely holds the post nicely whilst Daisy tears it through the bars.
We don't mind her chewing the brown envelopes, it's the stuff from Amazon, etc we don't like being ruined!
She also growls at ALL postmen, ALL neighbours and people wearing fluorescent jackets.
We are planning on getting an outside post box...