instal the new Mozilla Thunderbird 115.3.1

I understand you'd like to install the new Mozilla Thunderbird version 115.3.1.

Based on the text provided, it seems that version 115.0 was released on July 11, 2023, and there's an update available, which is version 115.3.1. You've checked your update histories, and according to UptoDown version histories, there were no changes made in 115.3.1.

To install the new Mozilla Thunderbird version 115.3.1, you can follow these steps:

1. Go to the official Mozilla Thunderbird download page.

2. Click on the 'Download' button for your operating system (Windows or macOS).

3. Once the download is complete, run the installation file and follow the prompts to install Thunderbird.

Before installing, make sure to back up your current Thunderbird data by going to File > Save As > Export > Mail and clicking 'Export Selected Folders.'

After installing, you can import your backed-up data by going to File > Open > Import > Mail and selecting the export file.

Please note that it's always a good idea to create a backup of your important data before making any significant changes or updates.

Let me know if you have any further questions or need help with anything else!

Instal the new Mozilla Thunderbird 115.3.1