Oops, it's T-bird 102.15.1 instead, my bad!

Look at settings>general and scroll down to the Disk Space area and adjust the compact setting to less frequentlly, and also consider checking the box to be asked each time.

David, Thank you. This sorts the issue sufficiently. I will mark this as solved.

As an aside, I've set a reminder in my phone to compact monthly. -- Cheers, John

You're welcome. I was glad to assist. And I agree with your premise: never upgrade just fix a problem; the problem just gets worse. :)

If only Thunderbird didn't change the look and feel of my installation I would upgrade regularly. However, because they decide they know better what layout I want, I edited config to stop automatic updates.

I honestly don't believe they actually use the software - or - they would realize how impertinence it is to interject their ideas regarding layout on someone else with no fallback for the customer.

I do agree; I always liked version 91. It did everything I needed. But there are millions of users, and many like new things. The advantage we have is that we do not need up upgrade if all is working. Should you ever consider upgrading, I suggest experimenting with the portable version, as that leaves your setup untouched. I wish you well. :) I am a conservative user myself;; I use the ESR release and that works for me.

No, no, I've not make myself clear. I like new things. What I don't like is being forced.

So because the interface is how we interact with something, their deciding to unilaterally change my setup would be like Chevrolet deciding for the new models to place the steering wheel in the trunk and the brakes on the passenger side.

But what stinks is they could as easily respect me, and offer the choice. Perhaps show me the new interface and say; We think this look and feel is better, test drive it and if you don't like it, this menu item will put things back where they were.

This would be akin to skins, wouldn't it? Would this be a huge problem for programmers? All I request is respect! Anyway, this is the same reason I bought up several copies of Office 2003 when Microsoft decided the ribbon bar was their future. Me? I found it stole large swathes of screen real estate, which interfered with editing, which of course was the software's prime purpose.

Finally, you mention the portable version and the ESR release. Sorry but I am so stupid I don't even know what these are. Would you kindly tell me more, please? And I am not lazy, I researched both with this before asking with these being perhaps the best examples as regards the portable version:

1. https://www.reddit.com/r/Thunderbird/comments/1661mn5/where_do_i_download_thunderbird_portable_thats/ (but it does not explain why I would want the portable version). What is my benefit of a portable version?

2. So for my benefit, I read this https://support.mozilla.org/en-US/questions/1285834 (but I am not certain I need this as I don't use more than my one computer). Anyway, I am eager to learn of a benefit I can apply directly.

Finally, as regards ESR, I found this: https://support.mozilla.org/en-US/kb/thunderbird-esr (however, again, I am unsure how I benefit). Everyone around me depends on Gmail, or Outlook. I am the only oddball depending on Mozilla, so there's no organization, as such.

Anyway, it is very gracious of you to take time to explain these things . . . thank you. -- John

I do understand. You are using an open-source product, which means the code is not tightly held, and, because the product is free, the marketing strategy of customer support is different — it relies on donations. I speak only to you as a volunteer, and not as a spokesperson. With the audience being supported, there is constant flux in the code, attempting to add new features and keep fixing the ones that don't work. The approach works because users are free to not upgrade, and those who enjoy changes and new features.

I know of no email client that lets the user decline some features and then remove them: the approach is to explain new features prior to the download, and then download if user agrees. Thunderbird's default is to automatically do that, but the user can turn that off. Thunderbird also has the ability to revert to a prior release if the new version does not satisfy the user. There is also a beta version that can coexist with installed version to allow testing (and giving feedback to a development forum). But that will always be for the upcoming release, and of no value if you prefer using an older version. Still, when curious, you can visit https://blog.thunderbird.net/ and https://www.thunderbird.net/en-US/thunderbird/releases/ to read info on releases prior to upgrading.

A challenge you may eventually face is that, in upgrading, you may find that the only reliable update strategy is to not leap over any releases. For example, if you desired to get to the current release, you would be well-served to first upgrade to 115.0.1, then to 128.0.1ESR, and then to 140.0.1ESR, and then to 140.9.1ESR. Doing those steps ensures that any tweaks that require conversion are automatically applied for you. An issue that isn't obvious to users is that much of the code is 20 years old, and the developers are trying to rebuild that old code while also evaluating new features. In cleaning up the old code, there is a need sometimes to replace one service with another (such as the addressbook conversion from MAP to SQLITE with release 78). Getting rid of the old code is sometimes bumpy, but thunderbird is getting stronger. I think 102 was the first step in doing that, and 115, 28 and 140 have built on that. You can follow some of this at the blog at https://blog.thunderbird.net/

Thunderbird prides itself on change, so change is to be expected. I do follow some other email clients (emClient, Mailbird, and Thebat) and they look the same today as ten years ago. But they relay on payment of license fees and work to avoid any major updates that would send their customers elsewhere. Different market, different approach.

On your question, the portable is good if you must use PCs regularly that aren't yours, or if you prefer to have just one install and carry it with you from one PC to another. And, it's handy when you want to experiment with a newer version without impacting your active version. Most updates have info, and when there has been a major update, there is usually a web page that attempts to show the changes, such as this one for 115: https://blog.thunderbird.net/2023/08/make-thunderbird-yours-how-to-get-the-thunderbird-115-supernova-look/ and this page does attempt to educate users who update to the later releases: https://support.mozilla.org/en-US/kb/getting-started-thunderbird-main-window-supernova

On your ESR question, Thunderbird switched direction in 2025 by adding a monthly version to the annual version, renaming the annual to have the ESR suffix. This URL gives a brief overview: https://www.pcworld.com/article/2629380/thunderbird-136-officially-switches-to-monthly-releases-matching-firefox.html That was for 136, which is now 149. The thunderbird.net site now DEFAULTS to the monthly release, so if you do decide to upgrade, you must carefully select the ESR version.

So, in all those words, you're safe with 102. But watch for changes. If email providers change their requirements, Thunderbird must add the code to support it. Yahoo, for example, recently made some changes for server setup, and Thunderbird addressed it, but such unanticipated changes don't apply to older releases. Ok, 'nuff words. Take care.