title: Combining object properties in a OO way
body: <p>I have a situation where I must send mail A and sometime I have to send mail B, but there are also situation where I want to send a mail which is consists of a combination of mail A and mail B.</p>
  
  <p>For example mail A has as it's subject 'Subject of mail A'. Mail B's subject is 'This is the subject of mail B'. Now I have the situation where I want this as my subject: 'Subject of mail A / This is the subject of mail B'</p>
  
  <p>How can I achive this using an OO way? </p>
  
  <p>I already have two seperate classes for mailA and mailB.</p>