Yahoo Mail has been inundated with complaints from customers following web service troubles blamed on a "hardware problem" by the company.

Users of Yahoo Mail have been unable to access their inboxes for up to three days. Others claim to have been unable to use the service for up to a week. The email service has been received as much as 280 complaints per hour.

The problems started on Monday night, when users began to experience trouble logging into their inboxes, due to an issue in one of Yahoo's data centres. Yahoo first acknowledged the issue early Tuesday afternoon, stating that it was aiming to restore access in a few hours. By Wednesday, however, Mail was still down for some users.

"Scheduled maintenance"

The number of people affected is unclear as Yahoo spokespeople have been reluctant to comment. Judging by the level of activity on Yahoo's mail forum, the number could have been in the thousands. In the discussion section, hundreds of users have said they have been without mail access for two to three days.

Yahoo has also been sending mixed messages about the reason for the problems. Although putting the initial issue down to a "hardware problem", Yahoo users have been encountering sporadic notices that the website is on scheduled maintenance.

With more than 100 million daily users and around 281 million registered users, Mail is one of Yahoo's most important products. It was recently redesigned in October with a new interface similar to that of Gmail.

According to a recent report in AllThingsD, Yahoo has had a hard time getting even its own employees to use Mail. CEO Marissa Meyer has said that Mail is one of the top things she wants to improve to attract new users to Yahoo.