Utilize the input text as a context reference, choose the right relationship between Whistl 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.

The review was sparked by the withdrawal of Dutch company Whistl from door-to-door delivery of mail in June.

Answer: industry