Hi, I have ISPConfig perfectly installed on my VPS during holidays, everything works. SSL, Mail, webserver, RoundCube, except the ispconfig3_roundcube plugin. I fallowed and reviewed every steps on WiKi (github/w2c/ispconfig3_roundcube/wiki/Installation), but every time breaks with Soap Error: Could not connect to host error. The credencials created on Remote User are correct, also permissions. My config.inf.php $config['identity_limit'] = false; $config['remote_soap_user'] = 'myremoteuser'; $config['remote_soap_pass'] = 'mysuperpass'; $config['soap_url'] = 'mydomain.com:8181/remote/'; $config['soap_validate_cert'] = true; $config['plugins'] = array("jqueryui", "ispconfig3_account", "ispconfig3_autoreply", "ispconfig3_pass", "ispconfig3_spam", "ispconfig3_fetchmail", "ispconfig3_filter", "ispconfig3_forward", "ispconfig3_wblist"); My certificate is valid by Let's Encrypt. But also have tried with $config['soap_validate_cert'] = false; Also downloaded cacert.pem in /etc/php/7.4/ folder and pointed the full path on /apache/php.ini and /php-fpm/php.ini [curl] ; A default value for the CURLOPT_CAINFO option. This is required to be an ; absolute path. curl.cainfo = /etc/php/7.4/cacert.pem [openssl] ; The location of a Certificate Authority (CA) file on the local filesystem ; to use when verifying the identity of SSL/TLS peers. Most users should ; not specify a value for this directive as PHP will attempt to use the ; OS-managed cert stores in its absence. If specified, this value may still ; be overridden on a per-stream basis via the "cafile" SSL stream context ; option. openssl.cafile = /etc/php/7.4/cacert.pem As described on SOAP Erros in FAQ (github/w2c/ispconfig3_roundcube/wiki/Troubleshooting---FAQ) Regards!