Yahoo is rolling back security and anti-spam enhancements to its Webmail service because they interfered with users' ability to retrieve POP e-mail from external accounts.

Yahoo tried for about a week to solve the problem, which arose after it beefed up spam filtering and added SSL (Secure Sockets Layer) capabilities to Yahoo Mail's POP (Post Office Protocol) functionality.

However, whatever caused the problem has proven harder to solve than anticipated, so Yahoo has decided to roll back the anti-spam and SSL features.

The goal is to restore the affected POP retrieval capabilities and add the new features later, once the problem has been properly identified and solved.

Yahoo Mail is a company crown jewel and a key piece of its ambitious plans to boost advertising, increase traffic, attract more developers and better compete by giving its users a "social profile" dashboard to unify and manage their Yahoo services.

A week-long, ultimately unresolved problem affecting Yahoo Mail users hampers the turnaround effort and comes at a bad time, particularly with the upheaval around Microsoft's acquisition offer and a looming shareholder proxy fight to oust current board members.

The rollback of the SSL and anti-spam features is under way and will take "a few days" to reach all users, wrote Ryan Knight, Yahoo Mail Community Manager, in a blog posting Monday afternoon.

"What this means is that your ability to retrieve from these accounts should be completely restored, however it also means that we will be rolling back the recently added option to use SSL. If you have added an account that requires SSL, retrieval from that account will no longer be possible," Knight wrote.

Yahoo Mail user Mike Bradley, a Realtor from Littleton, Colorado, thinks Yahoo waited too long to pull the new features and could have done a better job communicating updates about the situation.

"As soon as there were reports of problems, they should have rolled back immediately instead of waiting a week. Also, they should have updated the blog more frequently," he said via e-mail Tuesday afternoon. "The most frustrating thing is to not know what's happening, and frequently updated communication could have made for a better interaction with those of us affected."

Bradley, who uses Yahoo Mail both for work and personal communications, first noticed the POP problems last Wednesday. "'Server busy' error messages lasted two days, then I started getting time out messages for two days, then I started to get mail slowly, but not all my mail," Bradley said.

He noticed that not all messages were making it to his Yahoo account because he also gets his e-mail on his cell phone. "That's still happening today, and this morning I got the 'server busy' pop-up error message again. It's slowly coming back to life but when I retrieve email, nothing appears in my inbox for 5-10 minutes after the 'checking e-mail' message disappears," said Bradley, an otherwise satisfied Yahoo Mail user since 1995.

Knight first acknowledged the problem in the Yahoo Mail blog on June 3, when he informed users that the company's engineers were already rolling out a fix.

The problem persisted, however, and on June 6 Knight wrote that, despite the fix, outstanding issues remained and that Yahoo would continue seeking a solution.

He also explained the new features whose rollout led to the problems: "Recently we made some changes to how external account retrieval works. Most notably we added SSL functionality (enhanced security technology), which many users have been clamoring for. We are also taking steps to improve spam blocking for messages that are being retrieved from these external accounts, by running them through more aggressive filters. Unfortunately we encountered some unexpected problems that lead to server errors or processes timing out for some users," he wrote.

On Tuesday afternoon Yahoo spokeswoman Kelley Podboy confirmed that Monday's blog posting from Knight contained the most recent information available about the issue. "We are also sending direct e-mail to all users who have recently enabled SSL external accounts to notify them of the change," Podboy said via e-mail.

Yahoo Mail has two POP-related services, according to Podboy. One is "POP in," a free service for retrieving messages from external accounts, which is the one affected. Another is "POP out," for downloading messages using a desktop e-mail application, such as Outlook, and accessing them offline. The latter service is unaffected by the problem and available as a premium feature to Yahoo Mail users who pay US$19.99 per year for the service's "Plus" plan, she said. Both services are available to users of Yahoo Mail Classic and the New Yahoo Mail.

Another Web giant faced technical problems in recent days: Amazon's main site had availability and performance problems on Friday and Monday.