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. During the import of the .pst file, Outlook will not be usable, so it is best to start this process near the end of the day. However, you can still access your email through the web during this time. Also, only a single .pst file can be imported at a time.
NOTE: Large .pst files may cause Outlook to crash or hang. If you have a large .pst file and Outlook crashes, restart the process making sure to choose not to import duplicate items. The process will continue where it was when Outlook crashed.
- Open Outlook.
- Close all .psts to be imported from the Outlook client. Right-click on your .pst in your folder list and choose Close Outlook Data File.
- Exit Outlook to assure the .pst files are free from any connections to the client.
- Relaunch Outlook.
- In your folder list, right click on Inbox and choose New Folder.
- Name the folder, such as pst folder contents, and keep the new folder selected.
- Choose File | Open & Export.
- Choose Import/Export.
- Select “Import from another program or file” and click Next.
- Select “Outlook Data File (.pst)” and click Next.
- Browse to your .pst file, select it, and click Open.
- Choose whether you want to allow duplicate items, replace duplicate items, or not allow duplicate items (recommended option). Then click Next.
- If you want to import the entire .pst file, select the main folder containing all subfolders and 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, and then select the checkbox labeled “Include subfolders”.
- Finally, select the option labeled “Import items into the current folder” and click Finish.
- The emails and subfolders will appear in your currently selected folder. Depending on the size of the .pst, this can take a few minutes to several hours.