Fun fact about BSTR, it uses memory before the string pointer to store the length.

From the CComBSTR documentation from microsoft: "The CComBSTR class is a wrapper for BSTRs, which are length-prefixed strings. The length is stored as an integer at the memory location preceding the data in the string. A BSTR is null-terminated after the last counted character but may also contain null characters embedded within the string. The string length is determined by the character count, not the first null character." https://learn.microsoft.com/en-us/cpp/atl/reference/ccombstr...

From the book ATL internals that I read about 24 years ago.

"Minor Rant on BSTRs, Embedded NUL Characters in Strings, and Life in General From the book ATL internals that i read about 24 years ago.

The compiler considers the types BSTR and OLECHAR* to be synonymous. In fact, the BSTR symbol is simply a typedef for OLECHAR. For example, from wtypes.h: typedef / [wire_marshal] / OLECHAR __RPC_FAR BSTR;

This is more than somewhat brain damaged. An arbitrary BSTR is not an OLECHAR, and an arbitrary OLECHAR is not a BSTR. One is often misled on this regard because frequently a BSTR works just fine as an OLECHAR *.

STDMETHODIMP SomeClass::put_Name (LPCOLESTR pName) ; BSTR bstrInput = ... pObj->put_Name (bstrInput) ; // This works just fine... usually SysFreeString (bstrInput) ;

In the previous example, because the bstrInput argument is defined to be a BSTR, it can contain embedded NUL characters within the string. The put_Name method, which expects a LPCOLESTR (a NUL-character-terminated string), will probably save only the characters preceding the first embedded NUL character. In other words, it will cut the string short."

I wont link to the pirated edition which is never than the one I read.

So if there is code in outlook that relies on the preceding bytes being the string length it can be the cause of the memory corruption. It would require a sesssion in the debugger to figure it out.

Eric Lippert's "Complete Guide to BSTR Semantics" explains this well: https://ericlippert.com/2003/09/12/erics-complete-guide-to-b...