It’s been a tumultuous week over at Yahoo, where a major outage for the internet company’s webmail client threw many students, professionals, and other constant web communicators into a frustrating situation for several days. The issue began on Monday night, when some Yahoo Mail users reported that the service was either down entirely or failing to deliver messages.

Even by Wednesday night, when service had been restored to most Yahoo Mail users, the webmail system was still experiencing difficulties, with many of the emails that had been sent during the down time still floating around in cyberspace and searching for their recipients.

Four days after the outage began, with most users finally restored to stable email service on Friday, Yahoo CEO Melissa Mayer publicly apologized for the troublesome outage. According to a report from PC World, Mayer never expected the outage to prove such a resilient and long-lasting problem. After the issue was brought to Yahoo’s attention on Monday, the mail team quickly addressed the issue and began working to get Yahoo Mail back up and running. Under normal circumstances, the system should have been fully corrected – with all emails reaching their recipients – by Tuesday afternoon.

According to Mayer, though, “the problem was a particularly rare one.” Different users were facing a smattering of different difficulties as a result of the outage, and Yahoo technicians weren’t able to pinpoint right away what was causing the problem. As a result, many Yahoo Mail users had to deal with a week without email. Those who use Yahoo Mail for work or school were undoubtedly greatly inconvenienced by the outage, especially considering its proximity to the end of the year and looming holiday vacation time.

Mayer estimated that about one percent of Yahoo Mail’s users were affected by the outage at the beginning of the week. That means about a million users were experiencing difficulties with the webmail client on Monday alone. That number probably grew over the course of the week, as well.

The outage came at a bad time for Yahoo, which has had difficulty retaining the loyalty of Yahoo Mail users this fall. In October, the company unveiled a redesign to their email system which made it look and function a lot more like Gmail. Users were upset that Yahoo was copycatting their main webmail competitors at Google rather than blazing their own trail and retaining what made Yahoo Mail unique in the first place.

Furthermore, the webmail outage wasn’t even the only technical difficulty Yahoo faced this week. According to CNET, the Yahoo Mail outage was followed by an outage for Flickr, the Yahoo-owned photo-sharing network.