Users of RPost U.S. Inc.'s e-mail service, which handles e-mail in the same legal fashion as the U.S. Postal Service sends registered mail, has cool new feature called SideNote. Zafar Khan, CEO for the Los Angeles-based company, says SideNote lets you provide "context" to recipients of an e-mail message who are being "carbon copied" (cc:) or "blind carbon copied" (bcc:) on an e-mail whose content is primarily addressed to someone else.

For those unfamiliar with the world of paper letters and memos, Khan explains that in the "old days" missive writers would scribble notes or add Post-Its explaining to people why they were getting cc'd or bcc'd on a given message. But in the e-mail era that flexibility vanished. To add context, he claims, people often call or send additional e-mails to people being cc'd or bcc'd to give the context for the e-mail. With SideNote, RPost users simply click on a button in their mail client and write a separate bright yellow note to either the cc or bcc recipient. That extra note does not go to the person or persons in the e-mail's "To" field.

It's a simple, but very clever feature. Recipients need not be users of RPost and can even get SideNotes with their Blackberries or iPhones. SideNote comes free with the standard RPost service starting today. RPost has plug-ins for Outlook, Notes and GroupWise mail clients. Pricing for RPost starts at $59 per 100 registered e-mails.