Apple mail support MBOX file format so you have to convert MBOX into PST file format, use a reliable MBOX to PST converter tool. For more information go throught the article: What is Apple Mail and Email Format that it supports? - Magus Tools Blog
Hi @michmos321
Go through this article How to Resolve “File access is denied” OST Error? - Magus Tools Blog . It helped me a lot to solve this MS Outlook OST issue.
