re :''Image resizer extension is the only reason I use Thunderbird'' Not heard of that as the sole reason for using Thunderbird. Most people use thunderbird because it facilitates reading and sending emails and they prefer the UI to paid for versions of MS Office Outlook. It's not that simple to go back to previous versions as since 68 there has been a different approach to profile use and version 78 saw a conversion of address book from .mab format to .sqlite. Many security fixes have been applied in recent months, so why would you prefer a product that is not up to date just to resize an image that can done anyway using software you can download to your computer. An Example: https://www.irfanview.net/ The author of that addon did not update the addon even for 68 let alone 78. It is not that simple to learn a whole bunch of new code and then spend alot of time completely rewriting all the code. It's not just an update. It's not just a couple of hours work, the author cannot afford that sort of time. Just look at the paultry amount the author received in donations over all those years. People just used the addon, but did not support the addon author to maintain that addon. I can understand his position. There was no auto update from version 60* to version 68* in the early days - see link below for details. Version 68.10.0 will auto update to 68.11.0 But Thunderbird has switched off all auto updates from version 68* to 78*. To use version 78 you would need to manually uninstall version 68* and download and install version 78*. * https://www.thunderbird.net/en-US/thunderbird/78.0/releasenotes/ * https://www.thunderbird.net/en-US/thunderbird/68.0/releasenotes/ If you had an auto update from 68 to 78 then you probably have some Updater Software on your computer that did it. I would not allow other updater software to allow updates, only let Thunderbird manage it's own updates. The addon you are talking about would be going back to versions in the 60 range and that is quite a while ago. Version 60.9.1 was the last one. You can get a download from here: * http://ftp.mozilla.org/pub/thunderbird/releases/60.9.1/ As there have been several changes, I would not use the same profile for version 60* or 68*. Profiles are not really backward compatible. I would advise you create a new profile and then copy the contents from the current profile into the new profile overwriting default files. You will discover the address books will not work because previous versions used mab not sqlite. In profile name folder you should see abook.mab.bak and history.mab.bak files. You would need to rename them by removing the .bak, so they are called abook.mab and history.mab files. You can force a backwards compatible mode. Please read the info at this link: * https://support.mozilla.org/en-US/kb/dedicated-profile-thunderbird-installation#w_what-happens-to-my-profile-if-i-downgrade-to-a-previous-version-of-thunderbird