from The Wall Street Journal.
Feb. 11, 2008
A widespread service outage hit BlackBerry users Monday afternoon. AT&T said it has been told by Research In Motion that the problem is with RIM's infrastructure, and is affecting all wireless carriers in North America. The disruption follows an outage last April that left millions of customers without email access.
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However, for what it is worth I've received messages until 4:10 PM CST.