Looks like the Nokia Messaging Client for S60 v5 devices like the Nokia 5800, has been released in Beta and is now available for download.
Nokia Messaging on S60 V5 delivers all the great features you’re know from Nokia Messaging, including Push email delivery, IMAP subfolders and mobilizing up to ten mailboxes including Windows Live Hotmail, Yahoo! and Gmail.

Some of the highlights specific to the S60 5.0 client:
Since this is a prelease you must pay careful attention to the installation instructions. BetaLabs is basically putting this client out to gather feedback for the final version for the S60 5.0 client that will come in May (Edit: Check comments for a bit of clarification on this part).
So if you have an S60 v5 device, go on over and Download Nokia Messaging.
Here’s a video introducing this version of Nokia Messaging, staring the man behind it all, product manager Davis Fields :
Just so you know, this is the same version that we talked about in our “First Look at Nokia Messaging on S60 V5” post. I’m really glad to see Nokia release the app in Beta. Now all we need is Homescreen Integration, and I’ll be a happy man.
Just one small clarification - we put this out there to gather feedback for the version coming out AFTER May... in between now and the release, we're localizing it into twenty more languages, fixing small bugs and doing QA testing. But besides that, you're right on track! Thanks!-Davis
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