Files with the .mbx extension are Outlook Express Mailbox files. Outlook Express saves email messages in MBX format when users create messages. Most MBX files contain email data that can be read by humans. These inbox files range from 2KB to 15MB.
The MBX extension also covers formats for other programs. For example, some MBX files contain MapInfo MapBasic code. Others have no consistent format and may be unsupported.
MBX files open with Microsoft Outlook Express on Windows devices. This email client software created the MBX format. Although less common, 7 other applications may support viewing or editing MBX files.
These inbox data files have “Low” popularity. MBX files appear infrequently on hard drives compared to other extensions. However, the format causes issues when users share MBX files. The recipient needs Outlook Express or alternate software supporting the unusual format.
Eudora
Thunderbird