(Telecompaper) Enterprise telephony specialist Mitel has offered to acquire Shoretel for USD 540 million. Its unsolicited bid of USD 8.10 cash per share is a 24 percent premium to Shoretel's closing stock price the last trading day before the announcement. The company went public with the offer after Shoretel's board rejected an initial approach. Mitel said it aims to be a consolidator in the business communications market and a merger with Shortel offers complementary market footprints, particularly in the US, where ShoreTel does more than 90 percent of its business. Mitel said its offer to Shoretel will remain open until 20 November and urged the company to engage in negotiations. Mitel CEO Richard McBee sent a letter to Shoretel's board of directors on 02 October and again on 20 October, outlining the proposal.