The government has authorized banks to supply emails relating to business with American clients, including the names of workers and third parties such as lawyers and trustees, the Tages Anzeiger reported.
The Federal Council has given its approval for banks to be able to supply information, "including data on bank employees and third parties, though not client data, directly to the US authorities," the Zurich paper quoted Mario Tuor, spokesman for the State Secretariat for International Financial Matters, as saying.
Swiss lawmakers last month approved a revised tax accord with the United States that eases banking secrecy rules, allowing Washington to obtain details of tax cheats from Swiss banks with greater ease.
The new treaty will allow US authorities to demand information on suspected tax cheats if the bank in question or its employers have acted illegally.
Parliament passed the treaty while Bern and Washington were in negotiations over 11 Swiss banks that the US has accused of helping American taxpayers hide assets.