Google has assimilated the hosted security and compliance features it picked up in its $625m acquisition of Postini into its corporate email service and more than doubled the capacity of inboxes to 25GB.

The free Gmail inbox offered to common webplebs remains at 3GB.

The Postini deal completed last month and today Google said it had bolted on Postini's better spam filtering, outbound content controls, policy reporting and visibility features. It's part of a wider move to plug the credibility gap Google Apps has with large corporations.

The web giant is now offering Postini's users a free trial of Google Apps Premier Edition, which normally runs at $50 per user per year, until June next year. It's aiming to woo the 36,000 business email clients to switch to its other hosted apps too.

Prior to today's announcement, Postini's wares were available to Google Apps customers as a third party extra.

Google says the tune-up is effective immediately, though its own information pages don't seem to have been updated yet.

The firm's coloured-ballsy bid to convince the world's major corporations it'll be better at looking after their data than they are has made little impact so far. More than 99 per cent of its revenues still come from advertising. It claims "hundreds of thousands" of businesses have adopted Google Apps, but doesn't provide any more detail.

The slow start hasn't deterred Yahoo! however, as it coughed $350m in September for Zimbra, a firm that makes open source hosted apps. Microsoft has barely dipped a toe in the water: its Office Live beta requires users to own a desktop licence for the pricey software. ®

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