icloud rejects mail from alpine?

[Roderick]

I sent an Email to an @icloud.com address twice, once
from alpine configured with gmail.com and once with alpine
configured with web.de, in both cases it was rejected,
I received the following link:

https://support.apple.com/en-us/HT204137

Then I sent it with gmail web interface and it was not rejected.

This is something completely new to me. At the end we can only
send Emails with the software / interfaces that these big
companies dictate.

Rodrigo

[Eduardo Chappa]

configured with gmail.com and once with alpine configured with web.de,
https://support.apple.com/en-us/HT204137

The page you reference clearly says that sending an email is no reason to
accept it. As you can read from the page, the relevant issue is the server
that sends the email, so when sending email use a server that is
configured in a way that iCloud accepts.