ok I found what I needed in the mail.css file.....
in case someone else may wish to adjust this as well!
Hello.
I was looking into this as well. Before going any further, I was wondering if
you had any success/progress with this. I currently can't live without being
able to adjust these columns. Anyway, I'd love to hear about anything
you might have already done in this area. If not, I'll pursue creating a grid
library which will make the columns dynamic. That way, the user can
resize/adjust the widths of the columns at will while viewing the message
list.
Thank you for all your time and consideration.