I appreciate the simplicity of hosting ChatMail versus a regular mail server. It's simpler, lighter weight, and better suited for the chat use case. It's basically the ideal messaging platform for my needs.
Quote from https://providers.delta.chat:
"Usually, it just works, but for some providers, you need to adjust the settings. In this case, click on “prepare” for details.
Please note that push notifications do not work with classic providers and esp. large classic providers often have sending limits and overzealous spam rejections. This can worsen the chat experience, as messages are delayed or missing messages may even disrupt groups."