For Exporting Thunderbird Files/Mails to AOL you have two ways automatic and manual. Let's Discuss both one-by-one.
Automatic Method:-
- Install Tool:- Obtain the Webbyacad MBOX Converter Tool from webbyacad.net.
 - Attached File:- Select your MBOX File by "Add File" Button.
 - Preview Mail and its Attachments:- Now preview your mail and its attachment your verify.
 - Select the File Format:- Choose the Saving Format EMLX.
 - Choose Saving Location:- Select the saving location otherwise it saves your File on the Desktop and Press the Export Button.
 
Manual Method:-
- Set Up Your AOL Account in Thunderbird:- Open Mozilla Thunderbird > Navigate to Options > Account Settings > Click on Account Actions and select Add Mail Account.
 - Use OAuth2 Authentication:- Go to the Server Settings > Under Security Settings, change the Authentication Method to OAuth2.
 - Importing Emails from Thunderbird to AOL:- Once your AOL account is set up correctly in Thunderbird, you can start transferring emails > Drag and drop emails or folders from your Thunderbird account into the AOL
 - Verify Email Synchronization:- After transferring, log into your AOL account via a web browser to ensure that all emails have been successfully synced.