Going back is not a supported process and may result in problems.

If you want the old toolbar look:

• right click in the open toolbar space at the top, pick customize - all your familiar buttons are there.
• remove the icons from the top of folder pane, the settings found in the three dots to the right of "+ New Message"

Thank you, Wayne, but I did not say I wanted to go back to the previous version. I said I need to change the theme to look like the previous version.

The new look has more of a 3-D, "popped out" effect. There is too much color. I don't like the blue circles showing how many unread messages. The text is too small.

I find the overall effect distracting and disturbing - it's more difficult for me to use. If it can't be changed, I'll have to find another email client or write my own.

My fix is to revert back to the older version and disable automatic updates. Bit of a faff as you then need to import your saved profile to get back all your settings.

Only way I could find to get the look of Thunderbird back to a usable form was to find and backup my profile folder (depends on your system as to where that is), then uninstall Thunderbird and go to this page that lists all the available versions to download (it is NOT user friendly!): https://archive.mozilla.org/pub/thunderbird/releases/

Download the version you want to get back to the look you're familiar with, then install it. After it's installed it will prompt to set up new accounts etc. Ignore that, close the tab and go to import, where you can import your saved profile (it may have a long and complex file name). Takes a couple of minutes then Thunderbird closes and restarts, hopefully with all you accounts, old emails, settings etc intact.

Only thing left top do is disable automatic updates in the settings, so you don't get caught again.

Thanks, purchases22.

I exported my address book. Uninstalled Thunderbird and re-installed an older version. Turned off automatic updates and exited without creating an account as you suggested. Then I copied these files into the new profile from the old profile: key4.db, logins.json, pref.js. Restarted Thunderbird and all my accounts were back. Then imported my address book.

Ty @purchases22 i will do that as well when i find out how to get it from the NOT User friendly system to get a older version .. i only use it to get my emails in since Hotmail (now outlook) became very user unfriendly So should be able just to uninstall this 1 and install older 1.. fill in the account settings again and have everything back