DM News reports that email services firm Return Path will announce its purchase of Bonded Sender, the whitelist email company that proposed last year to create a system of email postage to help stem the tide of spam.

Email security firm IronPort Systems is selling the division and will continue to support the product. IronPort will have a significant equity stake in Return Path. Existing clients of Return Path will have to pay extra to use the Bonded Sender system.

A study done in the middle of last year showed that Bonded Sender's system generated a fairly high percentage of false positives - instances where email recipients indicated messages were unsolicited, when in fact they were not. In such instances, the sender gets charged a postage fee that is subtracted from a deposit made before the mailing is sent.