BBC says new commitments to preserve the "character and heritage" of the country's post boxes have been set out by Royal Mail and Historic England.
There are some 85,000 boxes - the classic pillars and others mounted on walls or posts - across England, and about 115,300 in the UK.
Royal Mail pledged to manage, repair and conserve its network of post boxes in their existing locations.
It also set out how the organisation works to prevent damage or theft.