1. Start a command line with admin rights.

2. python -m pip install pywin32

3. C:\Program Files\Stackless36\Scripts>python pywin32_postinstall.py -install The path C:\Program Files\Stackless36\ should be replaced with the path at which your Python version is installed.

4. Test (admin rights optional) using python -c "import win32com" or python speak.py

   where speak.py consists of this text:

   import win32com.client
   
   speaker = win32com.client.Dispatch("SAPI.SpVoice")
   speaker.Speak("It works. Hoorah!")
   

Working fine on Python 3.6.4 Stackless 3.1b3 060516 (v3.6.4-slp:9557b2e530, Dec 21 2017, 15:23:10) [MSC v.1900 64 bit (AMD64)] on win32. Vanilla CPython hangs out here:

C:\Users\C\AppData\Local\Programs\Python\Python36-32>python.exe
Python 3.6.5 (v3.6.5:f59c0932b4, Mar 28 2018, 16:07:46) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import win32com.client
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'win32com'
>>> exit()

C:\Users\C\AppData\Local\Programs\Python\Python36-32>python.exe -m pip install pywin32
Collecting pywin32
  Cache entry deserialization failed, entry ignored
  Downloading https://files.pythonhosted.org/packages/d4/2d/b927e61c4a2b0aaaab72c8cb97cf748c319c399d804293164b0c43380d5f/pywin32-223-cp36-cp36m-win32.whl (8.3MB)
    100% |████████████████████████████████| 8.3MB 50kB/s
Installing collected packages: pywin32
Successfully installed pywin32-223
You are using pip version 9.0.3, however version 10.0.1 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.

Those errors suggest you are inside a Python environment. For example, the Python REPL starts with three chevrons, >>>. You don't want this. Run these commands outside of Python in the system command prompt either through Windows or Linux etc.

The following worked for me on Python 2.7:

> pip install pypiwin32

Also try the following from this post:

> python -m pip install pypiwin32

Win32COM is part of [GitHub]: mhammond/pywin32 - pywin32.
According to the (above) URL, the package is only designed to work on Win:

Python for Win32 (pywin32) extensions

So, this is Win specific (it was never intended for other OSes).

As for your question, technically you could install it on Linux, or OSX (it is possible with some manual steps), but that would make absolutely no difference, because (even if installed) it would NOT run on those platforms, as it contains (consists of) binaries (.dlls) that don't run (can't be loaded by processes) on non Win OSes.

Just looked at the comments: [MS.Docs]: Office.MessageCompose interface is available on OSX, but (most likely, if there isn't already a Python wrapper available) you'd have to write the bindings yourself (their examples are in JS).

Additional (generic) information

Some packages are only meant to work in specific conditions, based on restricting criteria like:

• Platform(s) (OS, CPU architecture)

• Python version(s)

• ...

even if not enforced by the installation mechanism (meaning they can somehow end up "installed" on platforms that they don't work on).
Anyway, such restrictions are (should be) mentioned (example for PyWin32 - see the red boxes) in package's:

• PyPI page

  

• Homepage

  

• Other resources (e.g.: package's doc page, if it has one)

Bottom line is that such a package will not work outside the conditions it was meant to run in (even if it can be installed), and more: when attempting to run it, will yield some error message that might not be very clear.

There are packages with such restrictions, but can be installed outside them:

• Win:

  • ComTypes

    • Error:

      [cfati@cfati-5510-0:/mnt/e/Work/Dev/StackOverflow/q064975918]> python -c "import comtypes"
      Traceback (most recent call last):
        File "<string>", line 1, in <module>
        File "/home/cfati/.local/lib/python3.8/site-packages/comtypes/__init__.py", line 28, in <module>
          from _ctypes import COMError
      ImportError: cannot import name 'COMError' from '_ctypes' (/usr/lib/python3.8/lib-dynload/_ctypes.cpython-38-x86_64-linux-gnu.so)
      

    • Fix (improvement): [GitHub]: enthought/comtypes - Improve error message on non Win

  • WConio2

    • Error:

      [cfati@cfati-5510-0:/mnt/e/Work/Dev/StackOverflow/q064975918]> python -c "import WConio2"
      Traceback (most recent call last):
        File "<string>", line 1, in <module>
        File "/home/cfati/.local/lib/python3.8/site-packages/WConio2.py", line 125, in <module>
          from ctypes import windll
      ImportError: cannot import name 'windll' from 'ctypes' (/usr/lib/python3.8/ctypes/__init__.py)
      

    • Fix (improvement): [GitHub]: Solomoriah/WConio2 - Improve error message on non Win

Related (more or less):

• [SO]: ImportError: No module named win32com.client (@CristiFati's answer)

pip install pywin32 didn't work for me but pypiwin32 did.