Exploiting buffer overflows in Windows

There is a known buffer overflow vulnerability in the SLMail 5.5.0 Mail Server software. Let's download the application (from the following URL: https://slmail.software.informer.com/5.5/) and install it in Windows by double-clicking the exe installer. Once installed, run it inside a Windows 7 VM, as shown here:

Let's now attach our running program to an immunity debugger and use a simple Python fuzzer to crash the program, as shown here:

The following screenshot depicts the loaded code once we have clicked on Attach:

Let's use a simple fuzzer written in Python to try to break this code:

Now, let's run the code to see where it breaks the email application and what the buffer values at the time of the crash are:

It can be seen that somewhere between byte number 2700 and 2900 the access violation exception occurs...