re : FYI: I did try 102 and 68 before asking this question.

Please note that as of version 68 changes occurred regarding a dedicated profile. Basically, it means it's not so simple to go back to an earlier version, so advised you have a backup of profile before upgrading just in case you want to downgrade. There is a method of starting Thunderbird using the Run command eg: thunderbird -P --allow-downgrade https://support.mozilla.org/en-US/kb/dedicated-profile-thunderbird-installation

Please note there have been several major changes in phases regarding the Address Book and Lightning is no longer an addon. Trying to use an older version after the address book has been altered can be a pain to fix. So do create separate exports of your address books just in case you need them. eg: Version 78 had change from .mab to .sqlite The .mab files were not removed but they did have the names changed eg: abook.mab.bak It would also mean the 'prefs.js' file saw a load of changes as well to point to those new files. There has also been other major changes in various files in version 102.

re :I also use a custom theme. I cannot use dark mode as I'm old and visually impaired and dark themes make stuff impossible for me to read.

As of version 60*, Thunderbird offers a default Light theme as well as a dark theme. The preferences/options can be set up to work with computer High Contrast themes. All addons including themes you choose to install are the responsibility of the person who created them and not Thunderbird. So you would need to check whether the theme you currently use is compatible for the version of Thunderbird you are thinking of installing.

re :I have a dozen email addresses. Each email account has a number of filters which move emails to subfolders on Local Folders. Basically, nothing stays in the inbox of the account. I use pop for inbound email.

If you use POP then all the downloaded emails are stored on your computer in the same way as they would be if stored in 'Local Folders'. The only difference is if they remained in the pop account then they would be spread over a dozen folders instead of just the one 'Local Folders' folder.

re :v52.91. is 32bit. I've downloaded the 64 bit v60.9.1 So my question is; Can I install v60 over the top of v52......

On Windows OS, Thunderbird win32 versions would get auto installed in this location:

• C://Program Files (x86)/Mozilla Thunderbird

and win64 versions would get installed here:

• C://Program Files/Mozilla Thunderbird

When version win64 first came out there were some problems noted for those who had previously used a win32 version. So developers forced the installation of win64 into the same old location in Program Files (x86). But recently, I've noticed the win64 getting installed in 'Program Files'. I've just fixed a problem for someone where this occured.

I would suggest exit Thunderbird if running. Access 'C://Program Files (x86)/Mozilla Thunderbird' folder and delete all of it's contents, so you are left with an empty 'Mozilla Thunderbird' folder. Then clear the computer 'Recycle Bin'

When installing v60.9.1, select the 'Custom' option and choose to install into same location:

• C://Program Files (x86)/Mozilla Thunderbird folder

re :I have moved my profile folder and my mail storage off the C:\ drive

If you have left the profile 'Thunderbird' folder in it's default locaton: C://Users/User name/Appdata/Roaming/'Thunderbird' folder. then it should still contain all the necessary files eg: 'profiles.ini' which would tell thunderbird program where to find the moved profile.

However, if Thunderbird starts up and has a problem locating the profile - it will ask you to create a mal account - do not do this. Instead, Create a new profile, give it a suitable name and click on 'Choose Folder' option so you can point it to use the original profile name folder.

The addon 'Manually sort folders' will work with all versions including v60.9.1, but you do need to make sure you have installed the appropriate addon version. https://addons.thunderbird.net/en-us/thunderbird/addon/manually-sort-folders/

As of version 78*: Minimise to TRay was introduced Address books - changed from MORK .mab to SQlite format. Lightning the calendar addon is no longer used because it has been integrated into Thunderbird. https://www.thunderbird.net/en-US/thunderbird/78.0/releasenotes/

Version 102* Too many changes to list :) https://www.thunderbird.net/en-US/thunderbird/102.0/releasenotes/

Info on encrypting : https://support.mozilla.org/en-US/kb/digitally-signing-and-encrypting-messages The wizard asks whether you want to sign all outgoing messages or whether you want to configure different rules for different recipients. https://support.mozilla.org/en-US/kb/openpgp-thunderbird-howto-and-faq

Thank you for the detailed response. You have covered much ground.

I think I will just install the 32bit version so it installs over the 52.9.1 assuming that will work, otherwise as you suggested I could just delete the %programfiles(x86)% folder contents and install the 32 bit version in the 32 bit folder?

I couldn't find any compelling reason to change to the 64 bit version, and since 64bit had issues in it's early days perhaps it's best I steer clear of it for now, though your reply was excellent in explaining the situation

PGP/Enigmail has a number of frustrating aspects (I won't call them bugs as I'm sure they are intentional). For example, every time I go to write an email Enigmail creates an empty folder on the root of my C:\ drive. I had issues with the VPN or the VPN had issues with PGP/Enigmail, the service is quite heavy on system reasources. Was it 4 or 6 permanently running additional processes? I think I was testing v78 when I tried that encryption - so a couple of years ago.

Hence I switched to S/Mime. No extra processes, no stray folders created, no VPN issues. It just works. With the "security settings from Address book" addon it's exactly what I need.

The theme I use has a dark space-themed color. The text is Light so I can read it. The light them in the browser and Thunderbird uses white everywhere and in some places I can't read the text.

At this point I'm only going to 60.9.1.

Although, as you've pointed out, given the issues I have with Enigmail, that seems the only roadblock to updating to 102. It's actually not - the dark theme everywhere, the square tabs and a couple of other annoying features are putting me off. I gather the theme issues start with TB95? At the same time as FireFox? So 78 and 91 are candidates, if I can find some support on customizing the tabs.

I have backups covered with a file/folder backup covering every Mozilla folder, and a boot drive image which includes the F:\ drive as C:\ and F:\ share the same physical media.

re : I think I will just install the 32bit version so it installs over the 52.9.1 assuming that will work, otherwise as you suggested I could just delete the %programfiles(x86)% folder contents and install the 32 bit version in the 32 bit folder?

If using the 32win then yes it should install over or if you first uninstall and then install 60.9.1 it should be ok.

I'm presuming you know where to get the 60.9.1 install for win32, but as others may read this question and require that information, I'll add the info.

• http://ftp.mozilla.org/pub/thunderbird/releases/60.9.1/

• Select 'win32'
• Select prefered language eg: en-GB is English British
• Then click on 'Thunderbird Setup 60.9.1.exe' link to download a copy.
• It may download to your 'Downloads' folder or 'Desktop' depending upon your computer settings.
• Once download is complete, access where it was downloaded and clickon the *.exe file to commence installation.

I did uninstall my win32 and then force the win64 to get installed in C://Program Files (x86)/Mozilla Thunderbird. Since then I've followed all the updates and I'm currently using 102.7.0

The current version is still getting some improvements, but generally has few issues. It has alot more functions and security updates etc than the versions you are using. Some things look a bit different and squared tabs is one of them. I was irritated at first, so I do understand your opinion, but to be honest I've just become so used to it, I do not really notice it any more. I still prefer the old Folder Pane folder icons but a bit of userChrome.css code soon fixed that. I've not tried to fix the tabs as that looks a lot more complicated.

Arrrgh!! Got me. The release notes at https://www.thunderbird.net/en-US/thunderbird/releases/ for all versions of the 60.x branch say nothing about non-curved tabs. It starts from 60.2.1. What I didn't see was the additional link tucked away at the top of the page pointing to the 60.0. That page says it changed to rectangular tabs and other "improvements"

I found out the hard way. After upgrading I had square tabs and I recalled there was no mention on the release notes.

They also seem to have removed the drag space. I had to close a tab, move the program to my other monitor, then re-open the tab.

Cant seem to find a Thunderbird subreddit (like FirefoxCSS), and can't find any CSS code to restore the curved tabs.

Back to 52.9.1.

I'm not one that "gets used" to things I don't like. I don't like it - I change it. If I can't change it I dump it.

Thank you for all of your valuable information and assistance. It looks like I'm stuck. My knowledge of CSS is abysmal and at my age teaching this old dog new tricks is probably too much to ask :)

I actually had a stroke of good fortune. After many hours scouring the web I came across some code snippets which helped restore rounded corners to the tabs. I spent a few days trying various things from the firefox userchrome.css to see if I could get the tabs exactly like the were in "the old days". No luck so far, but what I have now is 100 times better than the squared tabs.

I've got all the add ons working. I might actually be able to upgrade!