Utilize the input text as a context reference, choose the right relationship between Australia Post and mail from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Letter volumes fell 7.3 per cent with losses in the mail business growing to $381 million as Australians switch to digital alternatives, Australia Post said in a statement.

Answer: industry