[ubuntu] Recomendations for VOIP application?

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http://ubuntuforums.org – Hi, I have previously used Empathy for a "Skype like" application. That worked reasonably well on my old email address. I never used it that much though. I am now in a situation where I quickly need to set up a VOIP call facilllity with someone else. I need to do it using a hotmail address. We both messed around for hours last night and had major problems. I don't know how much was my/our fault in the set up but also it seemed Empathy was being a bit erratic. So I know there's a number of VOIP type clients out there. What do you recomend for one that works easily using hotmail a (Hardware)