Finding fewer emails in your AT&T spam folder? It may be a mixed blessing.

AT&T appears to have implemented new spam filters that are catching legitimate emails - but provide no warning to the intended recipients.

Over the past week, internet service providers, individual email senders and customers of AT&T-controlled email services have reported a sharp uptick in the number of non-spam messages that failed to make it into end users' inboxes. The reports coincide with a noticeable decline in the number of messages being funneled into junk mail folders, causing many users to assume the blocking of legitimate emails is connected to antispam measures AT&T has recently rolled out.

Michigan-based Deerfield.com is one of the ISPs affected. On Friday, Kevin Fortune, a technical service representative, discovered AT&T had blocked all email being sent from servers connected to its DNS2GO service.

"They just took the preemptive approach and blocked everything from one of our IP addresses, if not all of them," Fortune said. On Monday morning, he said he had conflicting information about whether email originating from his servers was still being blocked.

El Reg reader Brett Brennan, a Deerfield customer who found he was unable to send email to addresses maintained by AT&T, said his messages were no longer bouncing, but he hadn't yet confirmed that they were getting through, either.

An AT&T spokeswoman said she was investigating the reports.

Brennan and Deerfield.com are by no means alone, judging from DSLReports threads here, here and here. All these forums report a familiar pattern: people who get their email from Yahoo.com, PacBell.net, BellSouth.net, or other domain names controlled by AT&T noticed a big drop in the amount of spam beginning sometime late last week. But at the same time, many of these users also found they were unable to receive email from legitimate sources.

"I get my work via email, so to me this is not a trivial problem," an AT&T customer named Liz who declined to give her last name said in an interview. So far, she's discovered that email coming from a friend and her web host are both being blocked, but she worries prospective customers who try to contact her through her website are also getting blocked.

"If they can't reach me," she said, "I don't know it." ®