To show the size of each folder displayed in the Folder Pane do this:

via 'Menu Bar':

• 'View' > 'Layout' > select 'Folder pane Columns'

OR via 'Mail Toolbar' :

• 'Menu icon' > 'Options' >'Layout' > select 'Folder pane Columns'

Then you can select the 'Size' column. see image below.

To see size of individual email: Enable the 'Size' column header. click on icon located far right of column headers select the 'Size' option. see second image below as guide

Thank you Toad-Hall. I had problems following your instructions. Was looking for images on the email I got from Mozilla, but finally went to Forum and saw the images you refered to and I could make it from there. Thank you very much.

A general comment on this whole situation. This is the most obscure setup I ever encountered. There must be a simpler way to get this done. Needless to say information available thru Thunderbird itself is pathetic.

But Toad-Hall saved the day.

Thanks again Frank Grant