Email message locked in outlook 365

[1Steve]

I have an Email I received from a client that I can't open. There is a lock icon next to it. My IT department can't open it either. When clicked on it gives a message the user credentials don't match. From what IT can surmise the sender probably restricted who can read it. However they sent it to a group mailbox. Outlook seems to be saying you are not c2s, so you can't read this, only c2s can. But the group mailbox does not have its own login and password. No one can sign in as c2s the group. Everyone in the group as individuals received the email in their inbox but none can open it.

[#2 · Accepted solution]

@1Steve Hi, the possibility has been around for quite some time when it comes to OME/AIP, but there are some prerequisites.

New Enhancements to Office 365 Message Encryption with Azure Information Protection - Microsoft Tech...

Message Encryption FAQ - Microsoft 365 Compliance | Microsoft Docs

[#3]

@ChristianBergstrom  I just spoke with my IT guy and he informed me that he made a mistake when he said C2S was an office group. Instead it's an office distribution list that we are members of. The rest of what I said remains the same. Thanks