Sony started returning PlayStation services across the world this weekend, but users have complained about not receiving their password reset emails.
Due to the sheer number of people attempting to get new passwords, emails were not going through to customers immediately, the Japanese electronics firm said today.
Sony was even forced to turn off services for around 30 minutes to clear the queue.
"With the huge number of people coming back online at the same time and resetting their passwords, it is creating significant email traffic to ISPs," Sony said in a blog post. "The consequence is that some of the ISPs are throttling the emails."
"We are currently trying to resolve this, but in the meantime please be patient and refrain from submitting multiple requests."
The restoration of the PlayStation Network has not been seamless. Sony delayed the rollout earlier this month, saying it wanted to test the robustness of its new systems.
The company started bringing the PlayStation Network back online over the weekend on a country by country basis and the restoration continued today.
However, in Japan, the home of Sony, regulators refused to allow the network to be reinstated.
They demanded to see more information about the security measures put in place by the manufacturer before services were restored, according to a number of reports.
Following the breaches, which saw data of over 100 million customers go missing, Sony said it had upgraded its data security technology, adding software monitoring, as well as penetration and vulnerability testing systems.
"We know even the most loyal customers have been frustrated by this process and are anxious to use their Sony products and services again," said Kazuo Hirai, executive deputy president at Sony.
"We are taking aggressive action at all levels to address the concerns that were raised by this incident, and are making consumer data protection a full time, company-wide commitment."
