My Aperture Export presets are:
External Editor File Format is TIFF (16-bit)
External Editor Color Space - no profile selected
email - using mail
email photo exort preset - JPEG original size
I am lost with the question on "what settings are you seeing in Mail" which top right and what should I be looking for? Sorry I'm struggling with this!
I think, what Kirby meant, is this:
When you are exporting your images with "File > Share < Email", you should see a pop up menu in the upper right corner of the window that lets you chose the file size:
What are your settings there? You should pick "Actual size", if the Mail server will let you send 5 MB files. Quite often the limit is 2 or 3 MB.
Is "Mail.app" the Mils client you are usimng, or are using a different mailer?