It seems like your browser didn't download the required fonts. Please revise your security settings and try again.


Starting May 1st, 2018, we will no longer offer the ArchiveOne family of products. This includes all editions of ArchiveOne, ArchiveOne for Files, Max Compression, and Access Security Manager. If you currently hold a maintenance and support contract, you will continue to receive our award-winning support until your contract expires, or until May 1st, 2019, whichever occurs first. The license for ArchiveOne is perpetual; therefore the software may continue to be used independently without any updates or support indefinitely.

Understanding PST and OST Files

  • Last updated on

Microsoft Outlook uses two types of data files: Outlook Data File (PSTs) and Offline Outlook Data Files (OSTs). A PST is used for most accounts. If you are using a Microsoft Exchange account, your items are usually delivered to and saved on the mail server. To allow you to work with your messages even when you cannot connect to the mail server, an OST file is kept on your computer.

The primary differences between the two types of Outlook data files are as follows:

  • PST files are used for POP3, IMAP, and web-based mail accounts. When you want to create archives or back up your Outlook folders and items on your computer, such as Exchange accounts, you must create and use additional .pst files.
  • OST files are used when you have an Exchange account and want to work offline or use the default Cached Exchange Mode. This type of data file is also used for accounts that you set up with the Outlook Connector for (formerly Hotmail). OST files are always copies of items that are saved on a mail server and do not have to be backed up like PST files.


Last updated on