Woolworths has copped a $1 million fine for bombarding customers with marketing emails even after they unsubscribed.
The communications watchdog found the supermarket giant had breached anti-spam laws five million times over the 10 months to July 2019.
Australian Communications and Media Authority chair Nerida O'Loughlin said Woolworths' behaviour was inexcusable.
"Woolworths failed to act even after the ACMA had warned it of potential compliance issues," she said on Thursday.
Customers tried to unsubscribe from emails multiple times but kept getting them anyway.
Woolworths managing director Amanda Bardwell put it down to a technical error.
Ms Bardwell said further breaches were a result of multiple rewards-scheme members sharing the same email account.
She said they unsubscribed individual members when asked, but didn't know it meant unsubscribing everyone who shared the email address.
"The ACMA has made clear it expects all communications to an email address to stop in such scenarios," Ms Bardwell said.
The $1 million fine is the largest ever issued by the communications watchdog.
Woolworths is appointing an independent consultant to ensure compliance with spamming laws, with staff to undergo training.
Ms O'Louglin said the fine should serve as a warning to other companies.
"Australians have the right to unsubscribe from marketing emails that they do not want to receive," she said.
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