When you need old DBX emails in Outlook 2019 quickly, the key is to skip the manual email-by- email transfer. DBX is an Outlook Express format, so converting the mailbox to PST first gives Outlook 2019 a format it can work with.
A simple route is to select the DBX file, scan and preview the mailbox and export it as PST. Mailvare Free DBX to PST Converter follows this approach and also supports attachments and mail properties during export. Once the PST is ready, you can open it in Outlook 2019 and check the migrated folders.