KnownBooleanMetadataFieldsUnmodified Field

Outlook email object associated metadata field. True if message has not been modified since it was first saved (if unsent) or it was delivered (if sent) (MAPI property PidTagMessageFlags 0x00000002 bit).

[KnownMetadataAttribute(IsEmailType = true)]
public const string Unmodified = "Unmodified"