I want to share what finally WORKED for me! First, let me explain that I lost dozens of hours chasing this down.
I was previously using Office 2010 and NordVPN. I recently installed Office 365 (2016), still under Windows 7, but I had issues that made Outlook in Office 365 unusable. Outlook would take up to 15 minutes to launch and open the profile (or would
eventually just fail altogether), and then after it had finally opened and loaded it would take on average about five minutes to open a new mail window when I’d hit Reply or New to send an email. The same issues existed on two desktop machines and two laptops
machines, with both Ethernet and WiFi, all with a rather fast connection.
I tried almost every approach suggested in this forum thread and by NordVPN support: TCP, no CyberSec, default gateway, restart Network Location Awareness service… None of it worked (or if it did the effect was extremely short-lived and the issues
came back).
It even got to the point that NordVPN tech support gave up on their efforts to resolve. They sent me an email citing a Microsoft tech article indicating that it's not fixable, and that ended that (well, they again gave it a shot by requesting
full diagnostics but then never got back to me after I sent them, and it’s been a few weeks now).
I finally RESOLVED it by trying what a user in this forum thread suggested.
I went to Hotspot Shield (Premium). That’s fixed all the issues for me, all at once!
It's a bit more money than NordVPN but, my goodness, it's a hundred times better than NordVPN was in every way in addition to the fact that Outlook works absolutely perfectly! (And so does OneDrive, which I hadn't bothered to even try before
when I had NordVPN, and which other forum posts indicated was also problematic with Office 365 when using a VPN – Outlook, OneDrive, and OneNote apparently had the most reported issues, which I assume is because of requiring such close interaction with the
servers.)
With Hotspot Shield, it's as if I didn't even have a VPN! It connects almost instantaneously (NordVPN could take some time), it doesn't bother me with choosing servers (I can choose countries, though I've never once had to -- while for quite
a while with NordVPN I'd often have to choose Canada even though I'm in Florida in order for Amazon to work properly), the banks all accept it fine so far, and overall I never even have to think about it being there.
The only issue is once in a blue moon in Windows or Android it disconnects when the Internet connection is lost and fails to automatically reconnect (though the Kill Switch works well in Windows and so far it has always automatically restarted
when the Internet was back in Windows and it’s only failed to do so once in Android after the WiFi connection came back).
Research into Hotspot Shield before trying it indicated they're definitely not the service to use if one wants total anonymity. The key players behind the company range from major Wall Street and Silicon Valley investors to tech experts formerly
with very high levels of the US government, and they make no pretense about providing the kind of anonymity that prevents the authorities from discovering who you are and your whereabouts. On the other hand, with those kinds of entities behind them, they've
apparently been able to create an entirely new, proprietary VPN protocol from the ground, which is apparently what accounts for this remarkably different user experience than what I had with NordVPN.
Without the paid Premium service, it's free, but the free version entails putting up with ads (and probably entails other performance and service compromises compared to the paid service).
I've had it on all my computers and mobile devices for a few weeks now. I’m thrilled that I found it and went with it (thanks to the other user on this forum). I can now use Outlook (and OneDrive) in Office 365! Without it, well, I was simply
not able to use Outlook in Office 365, period. (I live at a “hotel” and therefore must use a VPN at all times.)
I should mention that in doing research I looked at vpnMentor and they recommend NordVPN and Express VPN as two of the best, and I noticed a TV ad for Express VPN a couple days ago, so perhaps Express VPN is worth trying as well. I never tried
it. (I’m kind of assuming it uses the same core protocol as most VPNs, and I noticed quite a few of the “positive’ reviews said it can sometimes be a bit slow in connecting and they suggested choosing a server that’s closest – none of which I have to deal
with or even think about with Hotspot Shield.)