Problems with Yahoo! Mail are continuing today after emails sent during yesterday’s outage failed to arrive in customers' inboxes.
Angry customers took to Twitter to voice their frustration after the service - which is said to handle 26 billion emails a day - went down for much of the day.
While people can now check their inboxes, many have found that vital communications sent during the down period were not there.
Heidi Miller said: "I can get into my emails but I know I had emails sent between 7am to 2pm yesterday that I haven’t received?"
Yahoo! was telling people to wait and hope the missed messages would show later.
Yahoo! said that the service was back up at around 2.30 on Thursday.
They tweeted: "Most services are back online. This is a technical issue that affected our services. We are sorry for the inconvenience and thank you for your patience as we get everything back up and running."
The outage on Thursday also affected Sky and Talk Talk customers, and struck the UK and Europe most significantly.
A spokesman for Verizon Media, who own Yahoo! said: "Yesterday we had a global outage that impacted several of our trusted platforms.
"All of our consumer services are up and running. This was caused by a technical issue related to a DNS error and we are working to troubleshoot any remaining issues.
"We are sorry for the inconvenience."
