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.
"We want to apologise to customers who are affected by the issue. We do our very best to make sure people's emails go through so we've got our best technicians on it because it's a priority to us.''
Radio broadcaster and columnist Kerre Woodham has been affected by the outage.
"As glaciers creep and continents shift, I wait for Xtra to ring - anyone else having trouble sending emails?'' She said on Twitter.
"Xtra has had an outage since 2pm yesterday and it still hasn't been fixed. Perfect timing when I have no voice.''
Hastings accountant Preston Epplett said his firm and its clients were still having problems with emails yesterday.
"I know that our largest client, a major Hawke's Bay firm, is so frustrated they are looking to move all business away from both Xtra and Telecom,'' he said.
"I am aware of numerous emails I have sent which are not being delivered.
"The cost to our business in lost time and opportunities has been large. Today we received three emails which were sent last Wednesday.''
He said it would be better if all emails, not some, were blocked.
"We don't know what is going and what is coming _ you organise your business around emails. I normally get around 150 emails a day and at the moment that is about 80 or 90. I don't know whether people are sending them or not.