With the larger email quotas you get on Office 365, we recommend you move mail from your .pst files (personal folders) to your Office 365 account.  This allows you to access all of your email no matter what computer you are using.

NOTE:   We have had reports that importing large .pst files can cause Outlook to crash.  If you have a large .pst file, you may want to consider moving the folders manually into O365 instead of importing them.  This might help with Outlook performance and prevent crashes.  You could also break the .pst up into smaller .pst files but that also requires moving folders manually into a new .pst file. 

See Using Outlook Data Files (personal folders) for more information on .pst files.

This option lets the user automatically import a .pst file using the Import/Export option. In most cases this will speed the process up and make it a bit easier for the user.  if you have a large . pst file, consider moving the folders manually.

  1. Open Outlook.
  2. Close all .psts to be imported from the Outlook client (e.g., right-click on your .pst in your folder list and choose Close Outlook Data File)
  3. Exit Outlook to assure the .pst files are free from any connections to the client.
  4. Relaunch Outlook 
  5. Choose File | Open & Export.
  6. Choose Import/Export.
  7. Select “Import from another program or file” and click Next.
  8. Select “Outlook Data File (.pst)” and click Next.
  9. Browse to your .pst file, select it, and click Open.
  10. Choose whether you want to allow, replace, or not allow duplicate items. Then click Next.
  11. If you want to import the entire .pst file, select the main folder containing all subfolders. Then select the checkbox labeled “Include subfolders” OR if you only want to choose certain folders, expand the Outlook Data File until you see a specific folder you want to import. Select that folder.  Then select the checkbox labeled “Include subfolders
  12. Finally, select the option labeled “Import items into the current folder” and click Finish
  13. The emails and folders will appear in your currently selected folder. If you need to make any final adjustments, simply drag and drop the emails and folders to the correct location.

This option lets the user manually open an Outlook Data File (.pst) and choose which folders to import. This can be a better option when the user wants to import only specific folders and subfolders within the .pst file.

  1. If your .pst is not already opened in Outlook, choose File | Open & Export
  2. Choose Open Outlook Data File
  3. Find your .pst file (either C: or H: drive), select it and click Open.
  4. In your Office 365 folder list, right click on your email address (or account name) and choose New Folder
  5. Name the folder (e.g., pst folder contents)
  6. Next, in the folder list, locate your .pst file and click the arrow to expand the list of folders.
  7. Select a folder and drag it to the new folder you just created under your Office 365 mailbox.
  8. Repeat for each folder you need to move.
  9. When finished, right click on the .pst folder and choose Close "foldername"
Article number: 
103948
Last updated: 
March 10, 2021