We have found that one of our users has not had all his emails uploaded to Gmail from Outlook i.e. there is an archive pst file we would like to upload.
How can I upload these missing emails from the PST file?
You can use Google Apps Migration for Microsoft Outlook (GAMMO) to do this. To download the tool, visit the following url: https://tools.google.com/dlpage/outlookmigration
Once downloaded, log in to the relevant Google Apps account and follow the migration steps. When the migration is running, if you need to disconnect from the Internet, we recommend you press the Pause Migration button, and then Resume when you're reconnected.
Read more about GAMMO here.
The screencast below steps you through the process.