Sachin writes - "I have few thousand email messages inside Microsoft Outlook (a pst file) organized in various folders. I know it is possible to download emails from Gmail to Outlook using POP3 or IMAP but is the reverse path possible."
Sachin is looking for a trick to archive all Outlook email messages (and folders) to his online Gmail account for two reasons - one is secure backup and two, he will be able to access his old emails from any computer.
Solution: It is quite easy to transfer Outlook emails to your Gmail mailbox. Here's a step by step guide:
Step 1: Enable IMAP in your Gmail account and then configure Outlook (or Outlook Express or Windows Live Mail) to sync with your Gmail address via IMAP. Read this guide.
Step 2: Import your Outlook PST file into a Personal folder that is different from your default Gmail Inbox.
To import, click File -> Import And Export -> Import from another program or file. -> Next -> Personal Folder File (.pst) -> Next.
Select the PST file that contains your email, then pick the email folders that you want to import in Outlook and click Finish.
Step 3: Select the Personal folders that you want to backup online and copy them your Gmail Folder in Outlook (see screenshot).
In the Folder List, right-click the folder you want to copy and click Copy Folder name. Click the Gmail Folder in Outlook to copy that folder in that location. You can repeat the steps as needed for other folders.
That's it. Your Outlook email will soon become available inside your online Gmail Inbox.
Caution: The migration from Outlook to Gmail can take a long time if you have very large Outlook pst file or if your internet connection speed is slow. Therefore, consider removing all large emails before moving them to your Gmail via IMAP.
Related: Is Your Outlook+Gmail Slow ?