Outlook is only free under the Office 365 trial program. When the conditions of the trial are complete, it is no longer free. eM Client is only free for personal use. Thunderbird is the only one of the three that is free under any conditions. But there is nothing wrong with free alternatives. 100% of the world’s top 500 supercomputers run on free operating systems. In that case free is better, not because of price, but because of performance and functionality. Otherwise why would it be used?