How do I set the finder column view to always display the "thin" column edges?

Question

Sometimes finder switches to display thick column edges. These screen shots were taken 5 min apart, after a restart.  I would love to know to to make sure it always displays the thin version.
Side note: does anyone know how to open new columns that automatically resize to fit the largest file name.....?    Having to constantly resize columns is really irritating.

Answer 1

it can not display what has not been downloaded, for them to be the same I assume you have chosen to leave messages on the server.
Date: is set by the sender and has nothing to do with a delivery date in Thunderbird. If Thunderbird is displaying the date the message arrived in Thunderbird, what is in the date: header?
Received: is a series of transmission points and following the instructions below will display the latest.
* Select Tools/Options from the main menu.
* Click Config Editor.
* If a warning displays, click “I’ll be careful, I promise!”.
* Locate the mailnews.customDBHeaders preference, e.g. by typing “dbh” in the Filter field. Double click it, or select and press Enter.
* If the preference was not set previously, type “Received” and click OK. If some extension has already populated the preference, add “ Received” to the end of the list of headers, separating it with space.
* Close the Config Editor and restart Thunderbird.