To convert a PST file to MBOX manually, you can use an email client like Thunderbird. First, configure your Outlook account with Thunderbird using IMAP. Then, move the emails from Outlook to Thunderbird. Once the emails are in Thunderbird, you can export them as MBOX files.
Alternatively, you can use the BLR PST to MBOX Converter Tool, a more efficient and straightforward solution. This software allows you to easily convert PST files to MBOX format without the need for an email client. It preserves all the email properties and attachments, providing a hassle-free conversion process.