How do I determine the size of my email with all images and attachments?

On Outlook for Windows

1. Always save a draft of the email (either using the menu icon or open "File" menu and select "Save") as this causes the size to be recalculated.
2. Then open the "File" menu and the size is displayed on the right

On Outlook for Mac

Unfortunately Outlook for Mac does not provide an easy way to determine the file size, but the following steps will give you an estimate that is a little above what the actual size is.

1. Open the message 
2. From the menu select File > Save As
3. 
4. Save the message as "Email message" to a folder on your drive
5. 
6. Right-click on the file (or Cmd Click) to open the menu and select "Get Info". The file size will be displayed at the top right:
7.