
The deal was originally announced in October, and will give Symantec a leadership position in the software-as-a-service market by integrating MessageLabs' technology into its Symantec Protection Network Team.
The company aims to use the combined expertise to accelerate the development of new hybrid online and on-premise platforms for IT professionals, as well as expand its customer support models across the Symantec technology portfolio.
This new development means that customers will have the choice of messaging security via software, appliance or hosted services.
"Symantec and MessageLabs have a common belief in the benefits of in-the-cloud services and how they enable customers to be protected from threats and enforce policy," said Adrian Chamberlain, chief executive at MessageLabs, at the time of the original announcement.
According to Symantec, the close of the acquisition means it now has double the market share of its nearest competitor in the messaging security space.