mboxPack is an interesting tool for all those users who work with various email clients, because it lets you convert emails in EML and TXT formats directly to the mbox format of
Thunderbird.
Thus all the emails you have in EML or TXT you can read directly in Thunderbird. The whole mboxPack process is very quick and automated, even though it always asks for user confirmation before completing the conversion.
To work correctly you need to previously install
NET Framework 1.1 or later.
Curiously it is available in many languages, including Catalan, but not Spanish.