This morning, Yahoo acknowledged that "a small number of users" were encountering delays in getting into their email accounts. The company was unable to specify the problem's cause.
But people using the free, Web-based email service countered that the glitch did more than slow things down; in some cases, it brought service to a halt.
Some Yahoo Mail customers reported being shut out of the service most of the day yesterday, with difficulties persisting into today.
Large portal sites such as Yahoo and Microsoft's MSN have long regarded free, Web-based email as a staple offering. As millions of people have signed up for such services, the portals have found themselves objects of frustration when services slow or stop.