Exchange is Microsoft proprietary email server software which allows you centrally barter your entire organization leveraging mail communication technologies. Exchange maintains all of its user mailboxes and storage groups in single data structure file with .edb as its file extension.
Exchange server prior to 2003 release maintains priv1.edb and pub1.edb files as default for storing user mailboxes and publicly shared data respectively. However later Exchange releases maintains single structure named mailbox.edb for all its data consolidations of all its user lists.
Exchange edb file can be corrupted due Microsoft Jet Engine database fetch errors on its multiple instances run or due overly abused publicly authored distribution lists with vague attachments incorporating executables. Whatever be the reasons recovering user mailboxes among others is huge responsibility on any Exchange administrators.