American and Canadian users of BlackBerry smartphones are now experiencing delays in sending and receiving e-mails as the service disruption entered its third day.

BlackBerry subscribers in Europe, the Middle East and Africa initially experienced downtime in the smartphone's e-mail and Internet services on Monday due to a problem at the Research in Motion's (RIM) date centre in the U.K. The problem was partly resolved but spread to the U.S. and Canada.

RIM customers in Canada complained that the e-mails they received were in batches and three hours old. Web browsing was also slow or not functioning.

RIM said the failure of its servers caused a backlog in e-mails and the Canadian firm is remedying the problem by delivering e-mails in batches.

RIM explained that its backup switch apparently failed to function causing a large backlog in e-mails. It apologized to customers for the inconvenience, according to CNET.com.

BlackBerry e-mails pass through RIM's data centres around the world allowing the smartphone maker to encrypt the messages for security. The encryption makes BlackBerry's service appealing to businessmen and corporate users.

However, the centralized messaging system has its weakness because service is disrupted regionwide and affects millions on BlackBerry subscribers when a server malfunctions.