Canadian firm RIM said it replaced a switch to restore its BlackBerry Messenger server, but problems persist, Britain's The Register reported Wednesday.
RIM, also called Research in Motion, said in a letter to business customers that a quarter of its customers were affected by the problems that have made e-mail and text messages intermittently available for three days.
The Register said those without their own servers -- a key target audience for RIM -- are the ones most severely affected by the problems.
Rival company Apple Inc. is launching its iMessage server service Wednesday.