I have received a .msg file as an attachment from a coworker. I am using OS X and there are no default programs to open the file. Does anyone know how I can open a .msg file on my Mac?
MailRaider is a program that should be able to read those files just fine. It's available for $1.99 on the App Store. It used to be free, so you might find old versions somewhere.
It should be able to read the files and even save attachments. You can find the documentation here (PDF).
Here's a caveat about files that don't originate from Outlook: