Should I choose my hosting company's mail server, or make my own mail server on my Cloud server? (for security)

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http://serverfault.com – I have a commercial website on an Ubuntu web server and my hosting company has a mail server for all its customers. For security reasons, do you think I should rely on my hosting company's centralized mail server for my domain's email? Or should I just set up my own mail server on the same Cloud server? Maybe I should use Google Apps' mail server for my own domain? Thanks in advance (HowTos)