The airline Flybe has been fined £70,000 for sending more than 3.3 million marketing emails to people who had opted out of receiving them.
The emails, sent in August 2016, advised people to amend out-of-date personal information and update their marketing preferences.
They also gave people the chance to enter a prize draw.
But the regulator said Flybe should have obtained people’s consent before sending the emails.
“Sending emails to determine whether people want to receive marketing, without the right consent, is still marketing, and it is against the law,” said Steve Eckersley, head of enforcement at the Information Commissioner’s Office.
“In Flybe’s case, the company deliberately contacted people who had already opted out of emails from them.”