1. Add a btnMail as a member of the org.adempiere.webui.component. CWindowToolbar class by adding the following line:

private ToolBarButton btnMail;

2. Add the following code in to the init method in the CWindowToolbar.java class:

btnMail = createButton("SendMail", "SendMail","SendMail"); //Line# 156
btnMail.setVisible(true);
btnMail.setDisabled(false); //Line#168 after all the toolbar buttons are initialized

3. Add the following code in to the configureKeyMap method in the CWindowToolbar.java class:

ctrlKeyMap.put(VK_M, btnMail);//Line# 277

4. Add the following method in to the org.adempiere.webui.event.ToolbarListener class:

/**
* Send Mail
*/
public void onSendMail();

5. Clean and build the adempiere_360 project.

6. Add the following code in to the actionPerformed method in the APanel.java class:

else if...