What Is a PST File?

How to open, edit, and convert PST files

What to Know

This article explains what PST files are, how to find and use one on your computer, and how to convert a PST file so that the emails can be used in a different program.

What Is a PST File?

A file with the .PST file extension is an Outlook Personal Information Store file that stores personal information used in Microsoft Outlook and/or Microsoft Exchange. They might include messages, contacts, attachments, addresses, and more.

Outlook Personal Information Store files have a file size limit of 2 GB, after which the email program might take a performance hit. You can make the file smaller with Oversized PST Recovery Tool (also called PST2GB). It will trim anything past 2 GB and make a new PST file of a proper size.

PST Files

Outlook Offline Folder (.OST) files are similar to PSTs except that they support larger file sizes and are used as a cache for Outlook's Cached Exchange Mode feature.

How to Open PST Files

PST files are most often opened in an email program that can use the data, like Outlook (more on how to do that below) or Microsoft Exchange Server. Outlook Express can import PST files, too, but it doesn't save information to a PST file like Outlook does.

To open PST files in Microsoft Entourage on a Mac, use Microsoft's PST Import Tool for Entourage.

You can open a PST file without a Microsoft email program by using PST Viewer Pro. Since it's not an actual email client, you can only use it to search for and open emails or convert and extract messages out of the PST file.

Email Open View Pro (we don't have a link for this one) is another full-featured tool that can open PST files. It supports exploring the PST file even without an email client on your computer so that you can export the messages in other formats like EML/EMLX, MSG, or MHT. It can extract emails only or the attachments, too, as well as make an HTML index of all the messages.

If you have a corrupted PST file or one that won't open, try Remo Repair Outlook PST.

Did you accidentally delete your PST file or wipe it during a format? Try looking for it with a free data recovery tool. Older Outlook PST files are one of those really important files that are easy to forget to back up.

How to Convert a PST File

PST files in their original format with the .PST file extension aren't compatible with a huge variety of programs. However, you can do some extracting or converting to make the embedded emails work in other programs.

For example, the best way to get your PST file on Gmail or your phone is to set up the same email account (Gmail or one you use on your phone) on your computer and then transfer the emails from the Gmail data file to the Outlook data file. Then, when you sync the email client with the email server, the messages are sent to Gmail, Outlook, Yahoo, or whatever other account you used with the desktop client.

The Email Open View Pro tool mentioned above is another way of "converting" PST data into other formats (you can convert every email at once or only specific ones you want). You can also save one or more emails from within the PST file to PDF or a number of image formats.

Stellar Converter for Outlook saves the PST file to an MBOX file on Windows and macOS so that you can use it with a different email program, like Thunderbird or Apple Mail.

Backing Up and Copying Your PST File

You can move your PST file anywhere you like, and even make a backup copy of it in case your current one is deleted or gets corrupted. However, you first have to find where the file is being stored, which you can see through your Account Settings screen.

See these directions for where to find Outlook's data files. Once you find it, make sure Outlook is closed, and then copy the PST file anywhere you like.

Another option is to use Outlook's built-in export function to save the PST file to your hard drive or elsewhere, like a flash drive: File > Open & Export > Import/Export > Export to a file > Outlook Data File (.pst).

Adding PST Files to Outlook

It's easy to restore a PST file in Outlook or add an additional PST file so that you can switch between data files to read other mail or copy messages to a different email account.

Return to the link above that demonstrates how to find the data file. During those steps, choose Add to add a PST file as another data file. If you want that one (or a different one) to be the default data file Outlook uses, just select the one you prefer and select Set as Default.

Still Can't Open It?

The .PST file extension shares a striking resemblance to a number of other file extensions, even though they aren't related and can't open with the same programs as the ones mentioned above.

For example, PSD, PSF, and PSB files are used with Photoshop but share two of the same letters as PST files.

Some other examples include PS (PostScript), PSV (PlayStation 2 Save), PSW (Windows Password Reset Disk, Password Depot 3-5 or Pocket Word Document), PS2 (Microsoft Search Catalog Index or PCSX2 Memory Card), and PTS (Pro Tools Session) files.

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