Email, Messaging, & Video Calls Email Archive Old Mail in Outlook and Keep the PST File Small Reduce the size of your PST file by Heinz Tschabitscher Writer A former freelance contributor who has reviewed hundreds of email programs and services since 1997. our editorial process Heinz Tschabitscher Updated on January 31, 2020 PonyWang / Getty Images Email Yahoo! Mail Gmail Tweet Share Email As the pile of mail you keep in Outlook grows, so, typically, does the time it takes Outlook to do what you want it to do. The PST file size limit looms. (The PST or "Personal Folders" file, of course, is where Outlook keeps all your data, including calendars, contacts, and emails.) Instructions in this article apply to Outlook for Microsoft 365, Outlook 2019, Outlook 2016, Outlook 2013, and Outlook 2010. A Small PST File Is a Fast PST File Either way, it pays to keep the size of your main PST file small and manageable. You can have Outlook do some of that using AutoArchive. Or you divide your messages between more PST files, which can be painless and swift. Archive Old Mail in Outlook and Keep the PST File Small To create an archive of old messages in Outlook separate from the PST file you use every day: Select File and choose Info. Select Account Settings and choose Account Settings from the menu. The Account Settings window will open. Select the Data File tab. Select Add. The New Outlook Data File dialog box will open. Select Outlook Data File and choose OK. Enter the name for the archive under File name and select the location where you want to save the file. Select OK and close the window. Move Mail to the Archive To populate your newly created archive PST, Drag and drop entire folders to the root folder newly appearing under Mail Folders. This is handy if you already have an Archive folder that contains, say, all of last year's mail. Just drop it into the archive PST. Alternatively, to archive individual items: Right-click the root folder named after your archive PST under Mail Folders. Select New Folder from the menu. Type the desired folder name. Make sure Mail and Post Items is selected under Folder contains if you want to archive emails. For archiving other items, choose the appropriate category. Drag and drop individual or groups of emails onto the newly created folder. To move all mail preceding a certain date in a folder (or nested folders), select File > Info. Select Tools and choose Mailbox Cleanup. Select AutoArchive from the menu that has appeared. Close the Archive PST File After you have archived all items, you can close the PST file in Outlook: Right-click the root folder of your archive PST under Mail Folders. Select Close "___" from the menu. Access Mail From a Closed Archive PST File To retrieve messages from an archive PST file you have closed: Select the File tab and choose Open & Export. Choose Open Outlook Data File. The PST file and its folders will appear under Mail Folders, ready for action.