Plenty of tools exist that allows users to convert emails from Outlook Express .dbx files and save it either as mailbox (.mbox) or individual .eml files. One of such popular tools is for example the free command line DbxConv utility.
Convert Microsoft Outlook Express e-mail folder file to Mail mailbox.
We have found 2 software records in our database eligible for .dbx to .mbox file format conversion.
Microsoft Windows software - convert dbx to mbox on Windows
A command line DBX to MBOX converter
Convert from dbx file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned dbx to mbox. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Linux/Unix software - convert dbx to mbox on Linux
An Outlook converter for Linux