"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."
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."