#1. Download and Install Mozilla Thunderbird Application
Step-1 Visit the official website (https://www.thunderbird.net/en-GB/) and download the Mozilla Thunderbird application.
Step-2 Click on the Free Download button to start downloading.
Step-3 Locate the setup and double-click on it to initiate the installation.
Step-4 Assign the desired destination for the installation of the application and press the Install button.
Step-5 At last, click on the Finish button to complete the installation procedure.
#2. Configure Yahoo Mail Account in the Thunderbird Application
Step-1 After completing the installation, launch the application.
Step-2 Now, you see an Account setup wizard. Provide the desired details (Full name, Email Address, and Password) and press the Continue button.
Step-3 Now, the IMAP option is enabled by default. Press the Done button.
Step-4 Now, you will be redirected to the Yahoo login page. Verify your Yahoo mail account and press the Next button.
Step-5 Enter your Yahoo mail account password and click on the Next button to proceed further.
Step-6 After that, click on the Agree button to allow Thunderbird to access your Yahoo mailbox items like email, contacts, etc.
Step-7 In the Thunderbird application, you will see that the Account has successfully been created. Click on the Finish button.
If Thunderbird Application is already installed on your PC, follow the below steps.
Step-1 Open the application and click on the Menu button at the top-right corner.
Step-2 Now, select the Account settings option from the list.
Step-3 Expand the Account Action option and select the Add Mail Account button.
Step-4 After that, perform steps 2 to 7 as mentioned in the previous procedure.
#3. Backup AOL mailbox using DRS Thunderbird Backup Tool
Step-1 Download and install the DRS Thunderbird Backup Tool. Run it as administrator.
Step-2 Expand the profile list and choose the required Thunderbird profile. Press Next.
Step-3 Now, you will see the directories of the selected profile. Choose the desired items and click on the Next button.
Step-4 In the Save/Backup/Migrate As field, choose the destination file format/email client as per your requirement.
Step-5 After that, select the migration options to customize the resultant.
Step-6 At last, click on the Convert button to start backing up your AOL mailbox.