William Hill has appointed digital marketing and tracking firm RedEye to use visitors' activity details to create targeted email campaigns.
The bookmaker will be able to segment its database using customer behaviour and transaction details for the first time.
The campaigns will also be tailored towards French, German, Italian and Spanish language site customers.
Peter Nolan, group director of marketing at William Hill, said: "This is the first time we've had a programme like this, although we've done a few initiatives in the past. Online gambling is increasingly competitive and we have to move to stay ahead."
RedEye will continue to handle the firm's site and media tracking, as well as its ad serving. It also tracks users crossing to the williamhillcasino.co.uk site. Paul Cook, chief executive of RedEye, said: "Having collected all this data over the past year, it's now time to see how it can be put to use."
William Hill reported operating profits of £11.3 million from its interactive operations for the half-year to 2 July.