If you have to export O365 mailbox to PST you can use tools in eDiscovery to perform the task. There are lots of blog posts out there on the process. My former colleague Louis Warren at itgroove wrote a very clear post about the required steps which you can find here (thanks, Louis!). In essence, you create a search in eDiscovery that collects all the information for a mailbox. It then gives you a “key” and a link to pull down a “ClickToRun” app. The app will create a local PST file of the discovered data. It requires you paste in the key in order to execute.
This is all well and good except that you might get tripped up if you are using a non-Microsoft browser! Let me explain …
I tried the export O365 mailbox to PST process with both Chrome and Firefox and hit issues with the downloaded app not executing correctly. I got messages regarding “security zones” that really didn’t make much sense to me until I thought of things in the context of IE. As we all know, IE has security zones set up that you access from Internet Options:
I added the O365 URL into Trusted Sites inside IE then tried the eDiscovery process again from IE. This time the downloaded ClickToRun app opened properly, requested the key and ran.
I can only surmise but I suspect the eDiscovery tool actually checks your local IE settings (probably in the registry). It expects to see the O365 URL in a “trusted” zone (Local Intranet or Trusted sites). If it does not then it fails on open.
After I ran the whole process I exited out of IE and the eDiscovery tool and tried a different PST export, this time logged in to O365 using Chrome (my usual browser of choice). This time I got a different error about the tool being installed from a “different location”. So I then tried the same eDiscovery run using Edge and things worked correctly. Trying after that with Firefox gave me errors like I got with Chrome.
So, the moral of this story is that you must use IE or Edge to perform this process, at least the download and execution of the ClickToRun app. You can set up the search in eDiscovery using any browser and, for that matter, any device. But in order to complete the process (download and run) you must finish (download and execute) with IE or Edge.