I installed roundcube on my website and the main reason is that I want to extract the message bodies of some emails. I am able to do an echo statement in the file rcube_message.php that gives me the details I want. I believe you if you use the following:
$this->app = rcmail::get_instance();
$this->conn->handlePartBody($this->mailbox, $uid, true, NULL, NULL, true);
where $this->mailbox is your INBOX and $uid is the message id.
The point where I got stuck is that I want to include a link on the body of the email similar to:

which is the red icon that opens the message on a new page. I want the
user to click on this newly created link in their email to store the information of the body in the database.
What I want to achieve is to extract some information from certain email bodies to the database.
Anyone that can give me some pointers? Will be highly appreciated!
Start by reading the plugin documentation: Doc_Plugins (http://trac.roundcube.net/wiki/Doc_Plugins) you should be able to do everything you need with the existing plugin hooks: Plugin_Hooks (http://trac.roundcube.net/wiki/Plugin_Hooks)
Thank you for the response, I will look at it and believe it will be most helpful.