Configure outbound email on a CentOS 6.3 server that has a fix public IP

Environment: - Operable CentOS 6.3 server with a fixed IP, not attached to a domain. Scope: - Goal: Configure outbound email, using sendmail, postfix or any other solution. - Method: Use an external SMTP relay such as gmail, mandrillapp, or other. - Requirement: The email service need not receive incoming emails. It need not have user mail accounts on the localhost. It only needs to send email messages sent by a software called DSpace (DSpace is a java opensource e-library software - see [login to view URL]). User Acceptance Tests: 1. Successful emails sent and received using the following command: mail -s Test < /dev/null 2. Successful emails sent and received using the following command: /usr/local/dspace/bin/dspace test-email Note: The DSpace software is already installed and running successfully on this machine. Deliverables: 1. A solution which successfully passes the User Acceptance Tests as above. 2. Brief documentation, i.e. a simple text file, which describes the solution.