I'm keeping a lot of old email archived in the OLM files (I was using PST in the PC). Unfortunately this is using 20GB of my 128 SSD and I'd like to move them in an external disk. What is the best way to do this?
The OLM file is a standalone file, so all that you need to do is move that file to your external disk. I have an external hard drive that I use for holding files that I want to keep but don't necessarily need daily access to. In the Finder, I drag the file from my laptop hard drive to a folder that I've named "Outlook archives" on my external hard drive.