OST/PST encryption/compression

[bphd]

Are PST/OST files compressed by default? Or can they be compressed at demand? With what they're compressed?

When I try to open them plain with a text editor, I find no readable text, whatever the used encoding

I read that they can be encrypted but that it's a not well implemented functionnality, that it require a special configuration by the administrators, and that it's not done by default. Am I right on this point?