The 'Composing' option allows you to choose whether you wish to compose a new message in a new window or in the same browser window.
Click the 'Composing' drop-down box to view the associated options. These options allow you to customize the way you compose a new message. The options are
'Compose Messages in New Browser Window': Select this option and click the 'Update information' button to compose all new messages and email in a new browser window. When you click the 'compose' link in the 'My Email' page a new window 'My Email Compose' pops up where you can compose the message.
'Compose Messages in the same browser window': Select this option when you don't want a new window to pop up to compose a message. When you click the 'compose' link in the 'My email' page the page is refreshed to a new page titled 'My Email Compose'.