Or set up your own mail server on something like a small AWS instance.
If you want to use insecure legacy protocols, then at least keep them close to the client, not up in the cloud, where anyone on the line can read your traffic.
This is exactly why I have a Pi zero installed into all my Amiga systems, to act as gateway/proxy between old legacy protocols (between Amiga and Pi, 15 cm ethernet or serial cable), and modern protocols (between the Pi and the big bad world).
