Yahoo said it suffered an outage on Thursday across its services, including Yahoo Mail.
"You may not be able to access some of our services, including email. Our top priority right now is getting this fixed", Yahoo Customer Care said in a tweet.
The tweet did not specify the number of users affected by the outage or its cause.
Outage monitoring website Downdetector.com showed that more than four thousand users had been impacted. Yahoo is owned by Verizon Communications Inc.
