With an aim to expand its services on smartphones, social networking giant Facebook has acquired MailRank, a year-old startup firm focused on prioritizing e-mail, for an undisclosed amount.

MailRank prioritizes e-mail so that the user can focus on the content that really matters. The company is considered as solution to the problem of e-mail overload.

The two co-founders of MailRank, Bryan O'Sullivan and Bethanye McKinney Blount, will join Facebook as per the deal.

"We are thrilled to announce that MailRank's co-founders will be joining Facebook in December...We'll be discontinuing the private beta of MailRank for outlook to focus on our new jobs," MailRank said in its official blog.

However, financial terms of the deal were not disclosed.

Earlier this month, Facebook acquired mobile application developer Strobe for an undisclosed amount. Strobe develops technology which help developers create and distribute applications that work on devices like smartphones and tablet PCs.

Some reports suggested that the Strobe acquisition was a talent hire, as Facebook was mainly interested in the company's founder Charles Jolley. He is also the creator of the SproutCore open source framework. Before founding Strobe, Charles was responsible for mobile application development at technology giant Apple Inc.