Rideshare giant Uber has been hit with a fine for sending two million emails that breached spam laws.
The media watchdog says Uber sent all those messages on a single day in January, failing to include an unsubscribe link in emails advertising an alcohol home delivery service.
Half a million emails were sent to customers who had already unsubscribed from Uber's messaging.
It also breached spam laws as businesses must get consent from consumers before they send direct marketing messages.
Australian Communications and Media Authority chair Nerida O'Loughlin said Uber had accidentally characterised the emails as non-commercial, leading to the breach in their spam obligations.
"An avoidable error has led to more than two million messages being sent without a way for people to unsubscribe," she said in a statement.
"Consumers are fed up with their wishes not being respected. People rightly expect to have choice over who contacts them for marketing purposes."
Uber has already paid its $412,000 fine.
Ms O'Loughlin said ACMA was particularly concerned about marketing involving gambling and alcohol.
"We are actively monitoring Uber's compliance and will not hesitate to take stronger action if it doesn't comply in the future," she said.
"This is a warning to all businesses conducting e-marketing that they should be actively and regularly reviewing their marketing to ensure it is compliant."
An Uber spokeswoman said the company had made a mistake in sending the marketing emails.
"We worked collaboratively with ACMA to address and resolve it," she told AAP.
"We apologise to everyone who was impacted by this oversight.
"We take seriously our obligations under the Spam Act, and we have introduced additional measures to prevent this from happening again."
The messages in question were contained to one day and were not sent to any users who had excluded themselves from being able to view or order alcoholic items on the Uber app.
