Claiming dibs on digital signature technology, RPost has sued its higher profile rival Goodmail Systems in a Los Angeles federal court saying Goodmail’s Certified E-mail Paper Suppression service infringes two of its patents.

It wants damages and an injunction and says other parties may be named.

It claims discovery may show that “Goodmail’s partners are not only using an infringing service but are using Goodmail technology in ways that make them collaborators in that infringement.”

Goodmail’s partners include AOL, Comcast, Telus, Verizon, BT Communications, RoadRunner Online and Yahoo, among others.

CertifiedEmail PS is Goodmail’s premium service and is supposed to validate the exact contents of each e-mail sent with a date and time stamp confirming when it was sent and when it arrived in the recipient’s server-level e-mail inbox.

It’s targeted at banks, brokerage houses, credit card companies, utilities, insurance companies and healthcare concerns, the folks concerned with regulatory compliance. It runs $30 CPM.

RPost, however, claims to have pioneered e-mail delivery proof services with its flagship Registered E-mail technology.

CEO Zafar Khan says, “Goodmail started up as a way for marketers to buy their way past the spam filters of cooperating ISPs. Like many people in the industry, we didn’t like that because it essentially creates a two-tiered e-mail system: one for paying spammers and another for everybody else. But if e-mail providers want to let corporate spammers into their users’ mailboxes, that is between them and their users. However, with the introduction of their Paper Suppression service, Goodmail crossed a line.”

“Clearly Goodmail looked at RPost and saw that there is an enormous market for serious businesses that need to have irrefutable proof for the delivery of important documents and they decided to go after that. But that is our turf and we mean to protect it.”

RPost’s core Registered E-mail provides the sender with legally valid and court admissible evidence that proves delivery and content for e-mail. Its widgetry includes eSignOff electronic signature and contracting services and SecuRmail HIPAA-compliant end-to-end e-mail encryption services.

RPost has collected 24 patents – dating back to 1996 – that broadly cover verifiable proof for e-mail delivery and value-added outbound e-mail processing.

Its patents have been granted in Australia, Austria, Belgium, Canada, China, Denmark, France, Germany, Ireland, Italy, Korea, Luxembourg, Mexico, Netherlands, Portugal, Spain, Sweden, Switzerland, the UK and the United States; with additional patents pending.

RPost is backed by Symantec among others.