On my android samsung edge s6 I added a new protonmail account. The phone alerts me saying the server doesn't answer.
Here the configuration I tried:
IMAP server: 127.0.0.1,TLS,port: 143
SMTP server: 127.0.0.1,TLS,port: 587
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IMAP server: 127.0.0.1,SSL,port: 993
SMTP server: 127.0.0.1,SSL,port: 465
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IMAP server: 127.0.0.1,SSL,port: 1143
SMTP server: 127.0.0.1,SSL,port: 1025
I has been always alerted that "it is not possible to connect with the server".
The app email manager is the samsung's default one.