Telstra has confirmed that customers experienced intermittent issues on Tuesday with logging into Telstra Mail, as well as sending and receiving emails, with the issue fixed on Tuesday night.
Telstra added that no emails were lost; they have simply been delayed in being sent and received, with some yet to be delivered.
"Some email customers may have been intermittently unable to log in or intermittently experienced delays in sending and receiving emails," a Telstra spokesperson told ZDNet.
"This issue is now resolved; however, some emails sent during the incident have not yet been delivered. These emails will be progressively delivered.
"We thank customers for their patience and apologise again for any inconvenience caused."
Telstra Mail customers complained over Twitter about the inability to access and receive their emails.
"Day 2 of messages saying my password needs to be put in ... no emails received," a Telstra Mail customer tweeted.
The telco launched its Telstra Mail service in May for home broadband customers using BigPond or Telstra.com mail services.
Customers were told they would experience only a "minor interruption" in services as they were transitioned over to the new email system.
Telstra Mail allows for 10GB of mailbox storage and is available on Windows, Mac, and all mobile devices and tablets. The service is included in the plans of those on an existing Telstra service on a contract, as well as for those on SIM-only month-to-month plans.
The Telstra Mail issues follow seven outages on the Telstra network during 2016: The first 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.