Its depend which mode you are using in Outlook. If MS-Outlook is connected to exchange server, then it will create an OST file (.ost extension) on the local system.
On the other hand, if the Outook is working single (without any connectivity with server) having a connection with any web based email account or IMP/POP3, then PST File (.pst extension) is the file extension for Microsof Outlook 2007.
The file extension for Microsoft Access 2007 is '.accdb'.
Some of the important file extensions of Outlook and Outlook Express are mentioned as below :Microsoft Outlook :Outlook Data File (.pst)Offline Folder File (.ost)Personal Address Book (.pab)Offline Address Books (.oab)Messages (.msg, htm, .rtf)Stationary (.htm)Rules (.rwz)Outlook Express :Outlook Express data file (.dbx)Email Files (.eml)Email messages as text files (.txt)Address book (.wab)Contact information (.vcard)Internet Account files (.iaf)
all data is generally stored in a single file with a pst-extension
.docx The extension docx is used in Word 2007.
.accdb is the file extension for Microsoft Access and has been used since Access 2007. The previous file extension was .mdb.
.doc
.DOCX
PST itself a file format of Microsoft Outlook email client. So, I think you are bit confuse about your query.PST file single file format which stores all the information of MS-Outlook such as emails, attachments, contacts, address and so on. Outlook uses the .pst extension to save their database.For more about Outlook PST Data File, go to the source link.
Microsoft Outlook stores all of a user's personal information (such as email messages, contacts, calendar events, tasks, and journal entries) in a single file that ends with a .pst extension. Often this file is named Outlook.pst.
xlsx is the main extension used for Excel 2007.
.pptx
extension .docx