BERLIN/FRANKFURT, Jan 17 (Reuters) - United Internet (UTDI.DE) subsidiary Ionos said on Tuesday it would undertake a prime standard listing of its shares this quarter on the Frankfurt Stock Exchange, as the web hosting company readies for an initial public offering (IPO). The offered shares are expected to come from the holdings of the subsidiary's two existing shareholders, United Internet and Warburg Pincus, with United Internet to retain a majority stake after the IPO, Ionos said. United Internet shares were up 1.8% to 22.23 euros in early Frankfurt trading. The intention to float document did not provide details on the target issue price or the number of shares to be offered. A source familiar with the matter told Reuters last week that Ionos could achieve a valuation of 5 billion euros ($5.42 billion) in a stake sale.

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