The safest way to recover inaccessible Outlook Express DBX files is to avoid opening the damaged files repeatedly because this can sometimes make corruption worse. DBX files often become inaccessible due to sudden system shutdowns, virus attacks, storage issues, or the old 2 GB DBX size limitation. In many cases, users panic when Outlook Express stops opening emails or displays folder errors.

One user faced this issue after their computer shut down unexpectedly during an email compaction process. After restarting the system, several important DBX folders became inaccessible, including Inbox and Sent Items. Since those folders contained years of personal and work-related emails, deleting them was not an option. They tried using the SysInfo DBX Recovery Tool to recover the damaged files safely.
Read more: https://www.sysinfotools.com/recovery/dbx-recovery.php