Millions of wireless customers who rely on the popular Blackberry e-mail service were inconvenienced earlier this week, as the Blackberry network operated by Canada’s Research in Motion experienced a massive failure on Tuesday night. Although customers worldwide use Blackberry, the outage was confined primarily to BlackBerry subscribers of U.S. mobile phone carriers, including AT&T, Sprint Nextel and T-Mobile. While technical difficulties impacted the delivery of e-mails and connectivity to the Internet, phone service on Blackberry handsets was not affected. Technicians were able to restore service by 4 AM on Wednesday, although many customers continued to experience problems throughout Wednesday as a consequence of the resulting data backlog. Declaring, “the root cause is . . . under review,” RIM promised to “closely [monitor] systems in order to maintain normal service levels.”