When EDB file become inaccessible due to various consequences such as corruption and damage etc, then its needs recovery and to convert to the appropriate format.

What are the reasons for EDB file corruption?
Following are the few reasons for Exchange EDB file corruption:
Exchange server failure
Anti- Virus software
Accidental Shutdown
Oversize of the database file
Hardware Issues

Professional solution for Exchange EDB to PST conversion:

EdbMails is a professional third party solution for the conversion of offline Exchange EDB to PST. It quickly recovers offline EDB file and easily converts it to Outlook PST format.
Recovers corrupt, damaged Exchange mailbox items
Supports recovery and export of unlimited mailboxes without any size limitations
Exports recovered EDB file into PST
Supports to save EDB in EML, MHT and HTML format
Exactly replicates the original folder structure after recovery and export operation
Supports selective mailbox export to PST
Provides preview of all the mailbox items before PST export.

For More Information: EDB to PST Converter