PeterForster In my environment those emails are backed up before they even put them into that PST. I've got about 35 TB of veeam backup data containing every email our company has received over the last 8 years since they launched that backup product. Online archiving in 365 and Veeam don't play well; it creates an additional entry for each 50 GB slice of online archiving data the user has in it. Then when you go looking for something they're all just called ">Peter Forster" or whatever so you have to search all of them to find what you're looking for.
We are not 'dependant' on PST as a company but the users are, it's how every office worker has learned to file their emails over the last 25 years, and we've got a lot of people who've been around that long. I am not interested in having to re-educate everyone just because MS wants to force more of our data into their cloud. Are there going to be costs to run security scans on that data like there is in Azure storage? Not right away there will be, everything these guys do is meant to get more blood from the stone, but that will happen later on down the road. There seems to be 2 camps here....the one you're in who thinks "you're still using pst files? how antiquated" and the one i"m in who would rather keep the status quo because it's worked since like 1997. I get your point of view but I feel both camps have valid points.