Posting an image would help people to understand what you are talking about.

The UI has not changed much in general terms, but if you were using a version that was very old - years out of date and TB updated to a recent version, you would see a few variations as new functionalities were added.

What OS are you using? What version of Thunderbird were you using? What version of thunderbird are you currently using? Are you talking about the Write window looking different? Did you install and use a different theme, but TB is using the default?

I am using Windows 7. I was and am using Thunderbird version 38.6.0. No, I am not talking about the Write window looking different. I am talking about the whole UI. No I did not install a theme, nor was I using one. However, I will happily find myself one, if this is what Thunderbird is going to look like from here on.

Thank you.

I'd back up Toad-Hall in being surprised that you see it as having changed. I see very little change from one version to another.

Personally I use themes that restore a somewhat old-fashioned look. I don't like the flat flavour of Windows 8 and 10, but I must say I don't see W7 as flat.

Here I am using the xpDefault 38.0 theme. I also disable transparency wherever I can. It's just messy and visually distracting.

I did ask if you could post an image of what it is you are currently seeing, so we could be singing from the same hymn sheet, so to speak. At this moment I have no idea exactly what you are seeing.

Then it would be useful for you to say what has changed from your point of view, because if you were using and I quote 'I was and am using Thunderbird version 38.6.0' then nothing at all has changed in Thunderbird. The last UI changes were some time ago, think it was version 24 or there abouts. Of course there are various themes that you can download, but remember those themes are created by other people.

However, your Windows OS can influence the appearance. 'Control Panel' > 'Personalization' > 'Window colour and Appearance' offers colour schemes. Maybe, the changes you see are influenced by your computer.

I'm on Vista OS and using the Thunderbird default 38.7.0 theme Here are a few images showing what I see. The first is the one I use. The others show how the 'Window colour and Appearance' can influence the view. There are more options, but I think you get the idea. As you are using Windows 7 maybe you have similar or a few additional options.

My Thunderbird looks like the pictures posted. No "real" tabs, no colorful icons. Before, I had colorful Icons and they were in different places. At first I thought I had lost my mind, but I am a long time user of Thunderbird, and now I keep moving the mouse to where I am accustomed to finding the Delete button, and it isn't there. I have concluded that my mind is intact. The UI has definitely changed.

There is no need for me to upload an image of my current Thunderbird. As I said, it looks like Toad-Halls. I wish I could upload an image of what it looked like a few days ago, but that is impossible. I can only think of one possible explanation for why Thunderbird's UI was different earlier. My Thunderbird version came with WordPerfect, and while it looked like the same old Thunderbird I was used to when I installed it, it might be that the office suite had something to do with the UI and/or the change to the UI.

@Zenos. No, Win7 is not flat. Only Thunderbird, and I agree about transparency. Useless.

At any rate, I will just find myself a nice colorful theme and install it.

I seriously appreciate the help.

Bye now.