Optus has begun the process of automatically unlocking its customers' iPhones over its mobile network to allow the devices to be used overseas.
Handsets prior to the iPhone 4 were "locked" to a carrier's SIM card, preventing use of the device on other networks.
This practice began with AT&T's temporary monopoly on offering Apple's original iPhone in the United States, and carried over to Australian carriers.
The network lock was a security measure enforced by Apple to prevent iPhones from being imported into territories where the device was not yet available.
Late yesterday afternoon Optus iPhone customers report being sent an SMS that read:
"Your iPhone has been Network Unlocked, to complete; backup/restore via iTunes."
The customers were directed to a web link to learn how to ensure purchased apps, music and contacts were backed-up during the process.
Optus' web site said it had unlocked the devices "to save you time in calling us and to give you the ability to use a non-Optus SIM card, including compatible overseas SIM cards."
The unlock will enable iPhone users to access more affordable data services and avoid roaming charges whilst overseas.
An Optus spokesman said the carrier had embraced the network unlock option – a capability introduced in the last iPhone update from Apple – as a response to customer feedback as the Australian holiday season drew closer.
Telstra offered to unlock iPhones on its Next G network in mid-October but required customers to contact it directly first to request the procedure.