This MSDN link provides a table that shows the allocation of specific tag range values ββto the intended destination of the MAPI property tag table .
The table indicates that 0x67aa000b is in the following range:
0x6600 0x67FF Provider-defined internal non-transmittable property
A value of 0x000b indicates that it is a Boolean type.
I assume that the provider in this case is Exchange Server? Unfortunately, I could not find a description of this property sign.
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