An easy way to convert bulk and large Outlook PST files to MBOX without size restrictions is Softaken PST to MBOX Converter Tool. The utility facilitates the safe PST Mailbox to Thunderbird MBOX file format conversion. Without opening MS Outlook, all emails and attachments from Outlook PST files can be simply stored into MBOX. The software supports all of the MBOX file email clients including Thunderbird, Apple Mail, Poco Mail, Power Mail, etc. It also supports all Windows OS variant, including 11, 10, 8.1, 8, 7, XP, and Vista. One can get the free demo version of the tool. Visit here: https://www.softaken.com/pst-to-mbox-converter