A software glitch shut down e-mail service for some BlackBerry users Friday, and delays were still being felt hours after the problem was fixed.

Research in Motion Ltd., the Waterloo, Ontario-based company that makes the ubiquitous mobile device, said no e-mails were lost in the shutdown that affected an unspecified number of customers in North America who subscribe to the BlackBerry Internet Service. Phone service and text messaging were unaffected.

However, even after e-mail service was restored, slowdowns persisted into Friday night as message backlogs were being cleared out. The company did not provide an estimate of when service would return to normal and did not specify the software problem.

"(Research in Motion) is continuing to monitor the situation and apologizes to customers for any inconvenience," the company said in a statement.

BlackBerry Enterprise Server, a higher tier of software geared toward large businesses, was not affected.

Service outages have been rare in the BlackBerry's eight-year history, but the outages that have surfaced have prompted angry backlashes against the company because of its lengthy silences about what caused them and the cryptic and jargon-laden explanations that eventually emerge.

Research in Motion waited two days after a major outage in April before telling customers that a minor software upgrade had crashed the system. The outage prompted grumbles from always-on users all the way up to the highest levels of business and government, including the White House and the Canadian Parliament.

More than 8 million people have BlackBerry subscriptions worldwide. The company has relationships with 270 carriers in 110 countrie