Blackberry users are facing another shutdown threat to their push e-mail service following a new patent battle in the US.
Mobile e-mail provider Visto has won $3.6m (£2m) in damages from its rival Seven Networks for patent infringement.
As soon as it won the case, Visto announced it would sue Blackberry manufacturer RIM, claiming patent infringement. Visto also has ongoing patent cases against Microsoft and Good Technology for the same type of technology.
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RIM paid $612.5m to settle a similar, long-running patent dispute with patent-holding company NTP in March.
Before the settlement, the Blackberry service in the US faced shutdown.
Three of the four patents that Visto claims RIM has infringed are the same as those in Visto’s successful lawsuit against Seven.
Visto had originally sought more than $12m in damages from Seven in relation to six patents, but the court upheld only the claims linked to three patents.
Seven said it would be offering a workaround to allow its users to continue using their devices based on its push e-mail technology.
This was the same response made by RIM when it lost its case with NTP, but analysts said such a solution would have inconvenienced users and may not have worked.
RIM has so far not responded to Visto's lawsuit.