Visto, the Redwood City provider of mobile push email, said it got another $70 million in financing from DFJ ePlanet Ventures and existing investors.

That’s a horde of cash, especially for a company that has previously raised at least $80 million (UPDATE: In fact, Visto has now raised $230 million, as venture capitalist Bill Burnham states in his rant — he seems outraged — about how much money VCs are spending in this area).

Maybe it has something to do with the move by Sunnyvale’s Palm, maker of the Treo 650, to open up its phone to allow e-mail from competitor Research in…

Motion, maker of the Blackberry, and the fact that Visto is already in competition with other email programs, such as Seven and GoodLink?

With “push” technology, no longer do users have to tap-and-click their phones to check for new messages. Instead, emails appear on the mobile device the same way they do on the office PC inbox: automatically.

This was always going to be a tough field for the privately held Visto to compete in, but somehow we’re not surprised Brian Bogosian, Visto’s chief executive, is still slogging away. When we met him two years ago for coffee, he was one of the more confident CEOs we met (he was brimming with enthusiasm, even during the bleak days of early 2003).

Visto provides push email to companies like Vodafone, Canada’s Rogers Wireless and Sprint-Nextel.