I recently updated my MacBook Pro to a newer model. I started from scratch rather than migrate the old system image, and duly backed up everything.
I’ve had large archive files before from Microsoft Outlook for Windows (PST format), and found them to be easy to manage and portable.
Microsoft Outlook for Mac however cannot export PST files, but uses another format called OLM. OK, fine… but when I copied the 16GB OLM file to my new Mac and imported, I found that would take the best part of a week to import! That doesn’t really cut it since I need to carry to MacBook and use Outlook for work. Even Friday evening to Monday morning would not be sufficient to complete this.
After much Googling, I found out that most people recommend paid utilities that can do OLM to PST conversations.
Luckily I found another solution. It seems that importing the OLM mail archive and importing it on the same disk was causing the process to slow considerably. I just copied the OLM archive to an external USB-3 drive in order to import from there, and the whole archive imported in just a few hours.