Tiger Airways has been hit with a $110,000 fine for continuing to spam customers after they unsubscribed from marketing emails.
An investigation by the Australian Communications and Media Authority (ACMA) has found the airline failed to remove customers despite their repeated requests.
The emails also continued despite several warnings from ACMA.
The authority's deputy chairman Richard Bean said the action was another reminder to businesses about paying attention to what their customers were saying.
They also should test their email-unsubscribe facilities regularly, and not simply set and forget them.
Tiger had committed to making sure its unsubscribe facilities were functional and effective, Mr Bean said.
"Marketing to customers who have unsubscribed is not only against the law, it causes consumer frustration and that ultimately damages a business's reputation," he said in a statement.