It's an easy mistake to make, and one we've all done it before.
Forgetting to add those three little keystrokes at the end of an email- .au - and then getting a bounceback letting us know our communication has failed.
But for a staffer at NAB, what should have been a minor stuff-up has turned into a privacy disaster of embarrassing proportions, after the account details of 60,000 customers were sent to an adult website owner and domain name squatter.
David Weissenberg, an individual who resides overseas, is believed to be the owner of www.nab.com and the email address email@example.com, where the account details were accidentally sent due to "human error". (The intended recipient email address was firstname.lastname@example.org.)
Weissenberg, who lives overseas, has been linked with a number of registered domain names, including supersleazy.com, sexyneighbours.com and teaseclub.com.
His company Real Assets Limited is registered in the British Virgin Islands, according to the leaked Panama Papers database.
NAB wrote to customers last month apologising for the data breach, which took place in 2012 and exposed customer names, addresses, email addresses, BSB and account numbers, but not passwords.
The customers affected were those living outside of Australia at the time and holding accounts set up by NAB's migrant banking team.
The bank promised to monitor the accounts for any unusual activity, saying none had been detected so far.
Meanwhile, it remains locked in a legal battle with Google over the incident.
A spokeswoman for the bank told news.com.au it continued to work "cooperatively" with the internet giant towards resolving the matter.
NAB's executive general manager for international branches Peter Coad said the bank took full responsibility and was "working hard to improve and strengthen our processes to make sure this doesn't happen again".
"From our productive and helpful discussions with the email account owner, we understand that the email address to which the correspondence was incorrectly sent, is not actively used and our customers' emails have not been wrongfully used," Mr Coad said in a statement.
"Although this has been a complex process involving multiple international jurisdictions, all parties - including the email account owner - are taking this extremely seriously and NAB is working hard to resolve this matter for our migrant banking customers as soon as possible."