Email4Property operates nearly 2,000 property websites, each dedicated to a town or area in the UK.
The sites promote local estate agents' own brands and connect property-seekers with appropriate estate agents through the web, e-mail and phone.
Trinity Mirror has launched 10 local property websites since the start of the year and recently acquired Smart Media Services, publisher of SmartNewHomes.com. It also operates several local motors, recruitment and community sites.
Matt Brittin, Trinity Mirror's director of strategy and digital, said: "The service sits well with our local papers, local sites and SmartNewHomes, which together can help accelerate its growth and development."