PlusNet has been reported to the Information Commission for sending out 20,000 email addresses to 3,500 subscribers of its ISP brand, Force9.
The messages left subscriber names, email addresses and alternate emails visible to anyone who received it.
The message was sent to Force9 subscribers in .csv format, it included what products people were subscribed to, the price they were paying but not credit card details. Several irritated subscribers contacted The Reg.
At least one subscriber has complained to the Information Commissioner but the regulator takes a mimimum of ten days to decide what action, if any, to take.
Brian Trevaskiss, marketing manager at PlusNet, told The Reg: "We've emailed those customers to ask them to delete the emails. We've emailed the customers whose details were released and we've contacted the Information Commission too."
The mistake was the result of human error.
The ISP has had an unfortunate time with email lately - earlier this month it accidentally disposed of 700GB of customers' emails. ®