Terms of the common stock deal were not disclosed.
The acquisition gives Silverpop greater market share and additional technological capabilities, particularly in analytics. The Epigraphx name will be phased out.
Silverpop said the companies' integration will provide centralized research and development, sales and account management. Epigraphx founders Bob LaMar and Bill Thomas "will be involved in the merger, but the role is yet undetermined," a spokesperson said.