Thanks for your response as I took your comments on Python and figured out my issue. Short story was I needed to manually install a newer release of Python (v.2.7) that actually had the SMTPLib class/function. Once done and configured the SMTP feature works as designed.
But for the benefit of the forum, here is the longer answer. Upon receiving the response to my post, I realized I was running on an unsupported system (OS X 10.5.8 which has Python 2.5.1). The reason it wasn't generating SMTP traffic (or email errors) was that Python 2.5.1 doesn't support the SMTPLib function. That's why when they say OS X 10.6.8 is the minimum OS for WeatherCat, having a workable Python release is one reason.
I can't go to OS X 10.6.8 (Snow Leopard) on this Mac Mini, so I risked trying a Python upgrade. To compile the new Python binaries for OS X 10.5.8, you must first download and install the correct version XCode development toolkit from Apple so you can get makefile, gcc, kernel libraries, etc.. I chose version 3.1 which was in line for the OS X version I was running and the download took a while given the 1.04GB dmg file size. Once the XCode was installed, I then downloaded and installed PythonBrew which allows one to manage your Python distros on OS X. I used PythonBrew to download and install Python 2.7. Once installed I used PythonBrew to switch the default Python version from 2.5.1 to the newer 2.7 release. All worked well, except for the /usr/local/bin Python and Python config symbolic links which I corrected at the command line. Once done, I reloaded WeatherCat and tried my SMTP settings again. Worked straight away with a suitable version of Python.
Thanks everyone!
Alan