Thousands of Xtra emails have not been sent after two incidents affected the internet service provider in 10 days.
Last week, two of three Xtra routers were blacklisted by spam-blocking system Sorbs, meaning thousands of customers experienced outgoing mail delays.
Telecom social media manager Richard Irvine said this had been resolved. However, due to a "technical issue'' there had been intermittent delays in email delivery since yesterday morning.
Mr Irvine said he could not expand on what the issue was.
There was still a backlog of emails but Xtra was confident the issue had been resolved, he said.