I have some files that I want to give external users access to. I don't want random people having access either. I need to know how to do this and what the requirements are. Also these users may already have O365 accounts for their company, I am not yet sure.
Files to be shared must be secure
can live in a shared library
some external users on o365 for different organization
some external users not on o365
Please provide me with any documentation or instructions on how to accomplish this.