The storage groups and databases are the two elementary components of MS Exchange server. Storage groups are basically the containers used for mailboxes and public folder stores. Each storage group can contain multiple data stores and each data store is linked to an Exchange database.
When you install a new Exchange server in your organization, two data stores are created initially: a default mailbox store and a default public folder store. The default mailbox store contains two database files: Priv1.edb
: This is a rich-text database file that includes message headers, message text, and standard attachments.
This file contains streaming Internet content, including all audio, video and other media that are formatted as streams of Multipurpose Internet Mail Extensions (MIME) data.
In MS Exchange Server 2000 or above, all the inbound Internet-protocol traffic is stored in the .stm file by default. MIME messages always reach the Exchange Server as a stream of bytes, which in turn converts their header properties to RTF (Rich Text Format). This information is stored in the .edb file for use by the MAPI clients. If the MAPI client requests for another property or the whole message body, the Information Store (IS) changes that property to RTF and adds it to the .edb file. Thereafter, the message is permanently stored in the .edb file.