If you are trying to export Thunderbird emails using the manual way, please be aware that the manual process is a very difficult method that takes a long period to respond to you. To know the manual process, you must be a useful technical person. On the different hand, if you're examining, for a fast and straightforward solution to convert Thunderbird files to PST, Then use SysInspire thunderbird to outlook converter, which can simply convert many Thunderbird emails into PST format, including all attachments. Thunderbird emails may be converted to NSF, PST, EML, EMLX, HTML, GMAIL, and more formats. It also offers a free demo version, which allows you to test the tool before purchasing it.
Read More:- Convert Thunderbird Mail to Outlook