Yahoo Mail users are experiencing problems across the UK
Yahoo Mail is experiencing issues across the UK and Europe, with customers reportedly left unable to send or receive emails.
The issues first started around 13:30 GMT.
BT customers have also been left unable to access their email accounts. Yahoo currently runs the system that powers BT email addresses.
Independent website Down Detector, which measures social mentions around a certain topic to track outages across the globe, shows problems throughout the UK and Europe.
Enraged customers have flooded social media to complain about the problems.
"So Yahoo Mail is down! almost died" one Yahoo Mail user tweeted.
Thousands of users are experiencing issues with Yahoo Mail
Another posted: "Anyone having trouble with Yahoo mail?"
According to the latest crowd-sourced statistics from Down Detector, some 44 per cent of users have been left unable to login.
Meanwhile, 29 per cent and 26 per cent respectively are currently unable to receive or read emails on Yahoo Mail.
Yahoo Mail has not issued a statement about the reported outages.
By tracking mentions across social media, DownDetector shows the outage across the UK and Europe
This is not the first time the hugely-popular email service has had problems.
Last year, Yahoo Mail suffered an enormous outage, with thousands of customers left unable to access their email inbox for some 10 hours or so.
At the time, an administrator for Yahoo posted on a user forum, reassuring: "It has come to our attention that several customers are experience temporary errors or are about to start seeing them.
"This could be any error number as its a large outage.
"Our engineering team is aware and is working to resolve this issue as quickly as possible."
This latest issue comes at a bad time for Yahoo after it announced a major cyber attack.
The global tech firm recently confirmed that information from the large number of user accounts was stolen from its network in 2014.
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The data stolen may have included names, email addresses, telephone numbers, dates of birth and hashed passwords.
Yet the firm is fairly sure unprotected passwords, payment card data or bank account information was not included.
"Online intrusions and thefts by state-sponsored actors have become increasingly common across the technology industry," the company said.
"The investigation has found no evidence that the state-sponsored actor is currently in Yahoo's network."