i have been reading up and found that to see the messages sent the message body, I can run the command below in SSH however my server do not have exim how may I do so? any other way? Thanks.
That depends on what MTA (mail transfer agent) is installed on this server. Exim is just one of many and if you don't have it, you may instead have Sendmail, Postfix or Qmail. These are just the more popular ones and there are others. You'll have to check the documentation of the one that is installed on your system. If there isn't any, I'd recommend installing Exim. It's really powerful and flexible and it's what I use with my servers.
this server I am enquirying about has Courier Mail system. Any idea how to check sent messages on it? I've tried googling but still cant find yet on how to check.