Debug saml authentication via openssl

[jongra]

Hello,
After some debugging, the test.sh script runs smooth for given keycloak saml credentials - Many thanks to all of you writing issues in this project!

Now I'd like to login to a dovecot server using the
openssl s_client -servername dovecot -connect 127.0.0.1:993
command, followed by the imap command
1 authenticate plain "mailuser" "<Authtoken>".

This rises the error: [ALERT] Invalid base64 data in initial response
-> maybe because of the gzip compression?

Do I have to use another authentication method instead of "plain"?
Are there other ways to test the pam-saml authentication for dovecot?