Although its name makes you think it has to do with firefox, it doesn't. Foxmail is an email client that allows you to manage several email accounts at once, search for contacts, search for emails attending to sender, content or subject,...
It's very easy to use yet powerful enough. I would place it in the top five email clients with no doubt.
If I had to say something against it that would be that the help is not well translated into English but you are very unlikely to use it.
If the programs runs in Chinese, just delete the file chinese.lgb in the installation folder.