By Katie Marsal

Published: 06:10 PM EST

As much as the iPhone 2.1 firmware appears to have resolved many outstanding glitches with Apple's device, an increasing number of users say the update has broken background e-mail checks.

Dozens of users in Apple's support forums (1, 2) note that Mail in version 2.1 appears to drop frequent mail checks regardless of whether the device is set to fetch messages on a schedule or to push mail in real time. As a result, these users often don't receive e-mail until they check manually -- even for Exchange and MobileMe accounts that should respond almost instantly.

The problem occurs regardless of the particular iPhone model as well as the troubleshooting steps taken. While some have tried disabling the auto-lock feature to force the iPhone to stay awake, others have tried recreating accounts or restoring the phone entirely, all of which produce the same ineffectual result.

Most of those vocal about the problem, however, have discovered that the issue seems directly tied to the power state of iPhones. As long as the handset is active or plugged into a power source, it continues to receive mail at whatever rate its email settings would dictate. In a user's pocket, however, the phone appears to stop checking altogether until it's woken for use.

A few also report even a powered device failing to receive mail as long as the screen is blank.

Apple's response to the problem has been mixed. At least some customers say they have received acknowledgement from technicians that the problem is widespread, while one Apple representative has gone so far as to briefly join in the discussions and suggest troubleshooting steps.

"I just received a telephone call from the same product specialist, and he confirms that 6 other iPhones in their building are exhibiting the exact same problem," says one of the affected iPhone owners. "This is a global problem. This in their eyes is a 'major' issue and is getting escalated as we speak."

Even so, Apple hasn't as of yet chosen to inform all its technicians and is still asking Geniuses and other staff to perform normal troubleshooting, including phone replacements. For some customers, the lack of a more public and comprehensive recognition is pushing them to consider other smartphones that don't suffer the same e-mail issues.

"Funny how there are articles on loads of sites on how 2.1 does this and that and how great it is meant to be but no one outside forums is mentioning this," one British iPhone owner states. "My friends blackberry [sic] may not look as flash and may not do all the things my iphone [sic] can, BUT IT WORKS."