Sometimes it is handy to quickly see how large an email message is. You can modify or "customize" the view in the Outlook folders to allow for this:

1. Open the Folder you want to add the field Size. For example, Inbox.
2. Right mouse on one of the words located in the title area, such as To, Subject, etc.
3. Select Customize Current View.
4. Click on Fields.
5. Locate the option Size and click Add.
    Notice you can rearrange how the items are displayed in this screen, 
          OR
    Wait until after you have done the above steps and you can click, drag and drop the fields in an
    arrangement you would like.
6. Click Ok.

You should now have the field called Size listed as an option when viewing your incoming email. (On the web version, the size of an email is displayed by default.)