Users complain Microsoft Outlook fails to encrypt certain emails

by Milan Stanojevic
Milan Stanojevic
Milan Stanojevic
Windows & Software Expert
Milan has been enthusiastic about technology ever since his childhood days, and this led him to take interest in all PC-related technologies. He's a PC enthusiast and he... read more
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outlook encrypt mail bugs

Recently, Microsoft Office 365 users reported a weird issue affecting Outlook 2019 and on-premise Exchange servers. One user even created a Reddit thread to discuss the matter.

My company has an on-premise Exchange server and I often send encrypted messages through a Zix appliance. After installing the latest round of Office updates one of my customers noticed that an email that should’ve been encrypted wasn’t. So I look into and the email came from an address like [email protected] with my name on it. It was in my sent folder in Outlook but not in OWA. […]I’m pretty pissed off about this. I also run a spam filter for about 40 companies and I’ve seen a huge uptick in the amount of email coming from I do not like the idea of Microsoft stealing all of my sent email and running it through their servers.

Generally, the issue is experienced when you are using an on-premise/hosted Exchange server.

Apparently, the problem was introduced by the latest Office updates. Many people already reported the issue to Microsoft but the company has not fixed it yet.

Yes. I’ve found this out a year ago and reported it to Microsoft and our TAM. Countless emails and phone calls back and forth with support went no where. I eventually left the company I was working for, and to this day I can still spoof sending emails out as that company.

However, it’s a serious matter and Microsoft needs to do something about it. Today thousands of businesses use Outlook 2019 for communication. If the bug is not fixed, this situation can leave many enterprise users in a vulnerable condition.

How to Fix Outlook 2019 message encryption issues?

If you are one of those who are experiencing similar issues, follows these steps to fix it.

  1. If your Outlook program is already open close it.
  2. Now press Windows key+R to open the run dialogue box. Type regedit to open the registry editor.Run dialogue box
  3. One the registry editor Window is open, navigate to the following key:
  4. Finally, navigate to the right pane and create a new DWORD named “ExcludeExplicitO365Endpoint”.Create new DWORD
  5. Double click on “ExcludeExplicitO365Endpoint” to change its default value to 1.

Reboot the system to apply the new changes. Repeat the same process if you experience any such issue in the future.Have you experienced a similar issue on your system? How did you resolve it? Let us know in the comments section below.


Still having issues? Fix them with this tool:


If the advices above haven't solved your issue, your PC may experience deeper Windows problems. We recommend downloading this PC Repair tool (rated Great on to easily address them. After installation, simply click the Start Scan button and then press on Repair All.