Good afternoon, SITUATION 01 # I am in production with a Debain 11 server. 02 # For the installation of ISPConfig 3, I took this tutorial as support but without roundcube installation (-- no roundcube) : 03 # I use ISPConfig to manage domains, email addresses, etc. It's a configuration where all services are on the same server, using several domains. 04 # Each domain has its own certificate generated by "Let'sEncrypt" from "ISPConfig". On this point, everything is functional. The domains have been given an "A+" rating by "ssllabs.com". 05 # I've installed "Roundcube 1.6.0" ( "RC") after main install. 06 # I am trying to set up the server correctly to use IMAP (143) and SMTP (587) in STARTTLS only. 07 # Of course, in the "RC" configuration (config.inc.php), I have tried many configurations when the expected parameters by referring to the possibilities present in the "defaults.inc.php". Code: /var/www/roundcube/config/config.inc.php 08 # Nothing does it, except. I made a basic test in "25" without any authentication, the test mail went out of the server and was delivered to the destination server. 09 # In the files I publish here, of the configurations of each service, I have replaced the sensitive information by generic ones. 10 # I didn't touch anything in the "Postfix" and "Dovecot" conf files. Dovecot file conf header : My request What should I do/modify to set IMAP (143) and SMTP (587) with STARTTLLS ?[/B] Server Détails CONF FILES Index (See the contents of the 3 files, below in the first answer) Code: # 1 | (Roundcube) config.inc.php # 2 | (postfix) main.cf # 3 | (dovecot) dovecot.conf ENDING Thank you for your time to read and if you have a solution, I would appreciate it. Sincerely, Vincente.