How to bulk transfer MSG files into Thunderbird mailbox?

[JayJacob]

To bulk transfer MSG files into a Thunderbird mailbox, the most straightforward method involves using the ImportExportTools NG add-on for Thunderbird, as Thunderbird doesn't natively support this function. First, install the add-on from the Thunderbird Add-ons page. Then, select the target folder in your Thunderbird local folders or account structure where you want to import the MSG files. Right-click the folder, navigate to ImportExportTools NG, and choose the option to Import all messages from a directory (or a similar option for importing EML files, as the add-on often handles MSG by converting them to EML first, or you may need to first convert the MSG files to EML format using a separate tool before using the add-on). Specify the folder on your computer containing the MSG files to begin the bulk import process. 
Otherwise, get the EML Converter by MacUncle to transfer EML files straight to the Thunderbird profile folder. The tool will move the email messages without the need for additional software support.
For more details, check out the article - import EML files into Thunderbird.