The three-day BlackBerry outage has heavily hit Enterprise Server (BES) users and floored services for many, taking the damage even further than consumers and small businesses, originally said to be the affected groups.

The outage, which BlackBerry initially said was the result of a problematic network switch and an unsuccessful failover system, was originally seen as affecting consumers and businesspeople in small companies that link into the BIS consumer data centre.

But BlackBerry enterprise customers have confirmed they are experiencing serious problems.

Barry Gill, enterprise consultant at cloud email specialist Mimecast, said customers had contacted the company with their Blackberry Enterprise Server problems.

Compared to the initial reports, he said, "we at Mimecast have already seen a very different picture painted by our customers and services in use".

"We have had a number of customers report in to our support desk with BlackBerry issues with email delivery and enquiring about our Mimecast BlackBerry Continuity add-on."

Computerworld UK has also polled users in the UK on their experiences with BES. "We are getting emails intermittently, in batches," said an IT manager at a large UK company.

Another said: "I can't link in via BlackBerry Enterprise Server. It means I can't do my job."

Analysts have warned that BlackBerry customers were likely to consider looking for other devices when their contracts come up for renewal.

Richard Holway, a BlackBerry customer and chairman at analyst house TechMarketView, said it has been "a very, very long outage, much longer than any outage I have ever seen to such a service".

"It puts great questions on RIM, and I suspect customers will think twice about renewing their contracts."

"RIM has to be careful," said Francisco Jeronimo, research manager at IDC. "Apple is introducing products and services very similar to BlackBerry corporate offerings."