Twitter, the mobile messaging giant, said it had acquired RestEngine, a social marketing company specializing in emails, mainly to obtain its developers.

Financial terms weren't disclosed. The acquisition is the San Francisco-based Twitter's second recent purchase, coming only a few weeks after it acquired privately held Summify, which gives users summaries of relevant news from their social networks, as well as Hotspots, which concentrates on analytics.

RestEngine, founded in 2009, developed a platform to allow for targeting of advertising email based on a user's profiles and preferences. As well, it can detect when a user's interest is flagging and seek to re-engage him or her for further activity.

RestEngine had previously worked with Facebook (Nasdaq: FB), the No. 1 social network, to deliver email marketing messages.

Twitter CEO Dick Costolo last week said the company has 100 million users and a sound revenue model. The company raised $200 million last year from Kleiner Perkins Caufield & Byers and Russia's, and other sources.