"Our priority is to get your email accounts back up to speed as quickly as possible."
The problem stemmed from a bottleneck in the email delivery system, the company added.
"It is important to note that emails are being stored and will be delivered to customers as this issue is resolved."
Vodafone said it would provide a further update at 6pm.
The company has not said how many customers have been affected by the outage.
"Our tech guys have isolated the problem to one particular data centre and are working to fix this issue as quickly as possible," A Vodafone spokeswoman said.
"It is important to note that emails are being stored and will be delivered to customers as this issue is resolved."
Vodafone customer Ruth Lees said the outage was "major."
"We haven't been able to receive emails since Wednesday."
A quantity surveyor says the Vodafone meltdown is having a "crippling" effect on his business.
Chris Cooper of Fitzgerald Construction in Nelson said Vodafone had left his company in the dark.
"We are a Vodafone business user and not to have our email fully function is, to say the least, crippling to our day to day functioning and capabilities," Mr Cooper said.
"Once the email is up and running again we expect a serious backlog of work and overdue tasks notwithstanding any delays that this might now cause on our construction sites."
He said Vodafone had provided no information about when the issue would be resolved.
"You can check their website and obviously they've had a different message each day suggesting there's an issue - but no communication," he added.
"Three days is a very long time not to be able to undertake our day to day business for which we rely on email like many other people to communicate and distribute information."
Another user, Auckland man Chris Ryder, said he'd been having difficulties with the service since yesterday morning.
When he phoned the tech team yesterday, an automated message said the company was aware of the outage, and engineers were working on it as a high priority issue.
Mr Ryder said he had been a Vodafone customer for "years" and though there had been small outages before, there had been nothing like the current one that had lasted at least 24 hours.
Vodafone is yet to respond to the Herald regarding the issue, but a notice on the website says the company's fixed network is experiencing an "intermittent Vodafone email issue" which is affecting emails on smartphones, webmail and Outlook.
The site says the issue is under repair, but yet to be resolved.
On the company's Facebook page, a post from yesterday read:
"We are currently experiencing a technical fault which is impacting some customers ability to use their webmail, access their email via some email clients and also use domain hosted emails.
"We sincerely apologise to our customers for the inconvenience this has caused, we are working to resolve this at the highest priority."
Despite the message from the company, many users were still unhappy.
"Come on Vodafone. Been really patient, but trying to run a business from home and not being able to receive emails is getting quite hard," Karen Young wrote on Facebook yesterday.
"I have no idea if customers are contacting me or not. Not a good look when I try to give good customer service. I'm sure you are working on it but it's been nearly 24 hours now and that is not good customer service from a telecommunications company.
"Listening to your ad on the radio today telling businesses to switch to Vodafone to increase their profit. Really? Not happening here."
Telecommunications Users Association of New Zealand (Tuanz) head Craig Young said the outage was a reminder of how reliant Kiwis were on email communications.
"Outages like this remind us all of how dependant we have become on these electronic means of communication and how much we rely on our service providers to maintain robust and resilient systems."
He said the organisation had been made aware of the problem by a small number of users and has queried Vodafone about the issues.
"We understand they are working on the issue and we should receive an update sometime in the next hour or so."
Readers have shared their frustrations about the outage
"Not only smartphones but also landline. I have 4 email accounts, and have only been getting intermittent receiving on my landline, and very slow intermittent receiving on my iPad. When I do get emails downloaded I only get one of the four accounts. The next time I only get another one of the accounts. Their website on outages only mentions smartphones, not landline. Why not be honest? My problems have been since Wednesday. I have reset my modem to no avail.
- Barrie Jones
Still no email access (ihug) - ever since Wednesday! I know Vodafone is doing their best and working on it, but how long will it take!?
- John and Lisa
Worst failure in many years as an ihug customer. Email for many people has become an essential service and long term failure can be costly. The dishonesty that goes with it is hard to take. I tried two computers, both dual booted, reset the modem and logged into webmail. Email was not responding there either. The network "health" notice said nothing about it. I phoned and eventually got a reply, about 4.15pm, and got the run around to check everything as if I was the only problem customer! All it needed was some honesty like "sorry we have a failure" instead of wasting 15 mins with waffle. I have arranged a new email and won't be using Vodafone.
- David
I can send emails ok but can't receive incoming emails so I'm missing out on work coming in!!!
- Kj
Into day 3 and still no emails. Surely the engineers have some idea when the problem(s) will be fixed. We need an ETR - estimated time of repair. Just not good enough.
Robert Kelly.
I can cope (sort of) with no email since last Wednesday but what really annoys me is the total lack of information from Vodafone about the problem. Time to consider other ISP options.
- William
This is the third day in a row I have not been able to send or receive e-mails on my Vodafone account. Apparently it is a super serious problem effecting thousands of Vodafone customers around the country.
At least these days you can get thru to a human on the 888 number but all they do is tell you that they are 'sincerely sorry.' When I tell them that I am 'sincerely out of pocket', they don't know what else to say.
It's big news for me because I derive part of my livelihood from e-mail communication. Three hours I could just about handle, but three days....................
- Ross MacKay