Hi Paul, that's it. It worked. It was the "D" before the pin numbers. It works now and it sends the email when reaching 35 degrees. I have the Max6675 with 3.3V from the Arduino/Wemos Mini (or whatever it is what I bought).
I'll do what you said around the proto-shield to replace the breadboard setup and also have already ordered the other temp sensor, so I hope I don't have issues changing the Max6675+K-type with this DS18B20 one.
Thank you again for the very useful advice.