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Datran Media is launching an ad marketplace for publishers of opt-in newsletters and the marketers who want placement in those emails, reports ClickZ.

The Datran Media Exchange Online platform will allow publishers to list available space. Marketers will then be able to bid on placements across all available opt-in email inventory. The platform will provide advertisers with a number of performance metrics such as click-throughs and conversion rates.

The exchange is designed to bring Google-esque transparency to how well email ads are performing and recommend changes that could improve performance. Publishers will also have access to Datran's NetMargin affiliate network.