Terms of the deal were not disclosed.
eFax stock jumped 69.61 percent or 8.88 points to 21.63. The stock has traded as high as 14 and as low as 1.44 during the past 52 weeks.
The company said its fax-to-email services will be available to the more than 6.5 million members using Xoom.com.
The companies expect today's deal to produce new services for Xoom.com members sometime in the second quarter of this year.
Shares of Xoom.com, an Internet-based direct-marketing company that allows its members to build their own Internet home pages, moved 3.92 percent or 2.63 points higher to 69.63. The stock has traded as high as 77 and as low as 21.13 during the past 52 weeks.