https://learn.microsoft.com/en-us/openspecs/exchange_server_protocols/ms-oxmsg/05705862-f269-4d83-99b8-738a4f2ae9da?redirectedfrom=MSDN
[MS-OXMSG]: Applicability Statement | Microsoft Learn
The .msg File Format is used to store a Message object in a .msg file, which then can be shared between clients or message
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