Telstra has said that as a result of a fire at its Chatswood exchange, it is possible that customers' SMS messages have been delivered to people other than the intended recipients.
"As a result of the Chatswood exchange fire today, it's possible some SMS messages have been incorrectly delivered," a Telstra spokesperson said.
"As mentioned previously, customers won't be receiving SMS messages in the short term while we resolve this issue."
The telecommunications provider has not said how it will compensate customers for the privacy and security implications involved in SMSes being delivered to the wrong people.
Telstra's SMS outage has also affected internet banking services for both the Commonwealth Bank of Australia (CBA) and the National Australia Bank (NAB).
"Please note: Some customers are experiencing delays with receiving SMS notifications due to a mobile network outage," a banner on NAB's internet banking app says.
A Telstra customer also complained on Twitter about not receiving an SMS from CBA with their four-number PIN when attempting to get cash out.
Telstra earlier on Thursday confirmed on Twitter that customers were experiencing an outage across fixed-line and mobile services due to a fire at one of its exchanges.
"A fire at the Chatswood Exchange in Sydney this afternoon has been contained, but damage has been caused to some power infrastructure," the spokesperson added.
"As a result, a number customers are experiencing loss of service. Our technicians are currently completing a full assessment of the impact. We will provide more information as soon as it is available."
As of 3:15pm AEDT, Telstra said voice services are beginning to be restored; however, the telco added that SMS messages are not being received for the "short term". At 4:15pm AEDT, all voice services were restored.
"There is a related issue impacting SMS messaging. Customers won't be receiving SMS messages in the short term while we resolve this issue," the spokesperson said.
The issue follows seven outages on the Telstra network during the first half of 2016: The first almost a year ago, on February 22, which affected prepaid and post-paid mobile services and was caused by "embarrassing human error"; the second on March 17, which involved an hours-long national mobile data and voice outage; and the third on March 22, which was a smaller voice outage.
It then experienced an NBN and ADSL outage in May that resulted in the telco having to send free modems to customers still affected several days later; a mobile data services outage later that week; a broadband service outage in June; and an outage that took down businesses across Victoria, including banks, hospitals, department stores, and Jetstar.
As a result, Telstra CEO Andrew Penn in June committed the telco to investing an additional AU$250 million in its network over the next six to 12 months in three major areas: AU$50 million to be spent on improving mobile network resiliency by creating better real-time monitoring and speeding up recovery time; AU$100 million on increasing the core fixed-line network's reliability and resiliency; and AU$100 million on upping its ADSL broadband capacity to cope with demand.
The Telstra Mail service also experienced issues in August 2016.
Updated at 4:35pm AEDT: Added details on impact of SMS outage on internet banking.