I'm building a web app that uses PHPMailer to connect via to an ISPConfig SMTP server to send emails. The problem is that PHPMailer won't connect using TLS because my ISPConfig is sending an invalid certificate. I can hack PHPMailer so it will accept an invalid cert but would rather fix the problem so is there a guide for how to install a valid certificate for the ISPConfig SMTP server? I'm using ISPConfig 3.1 so it would be great if I can create a certificate by using the built in Lets Encrypt support.
First of all, you don't need smtps when the mailer is installed on the same server, just use localhost as mail host then without smtps. If you have a separate web and mail server, then smtps should be used indeed, the postfix smtp cert is set in the main.cf file, just replace it with a valid cert for the server hostname of the server. The Builtin letsencrypt system is for websites ony and not the postfix mail system.
Thanks Till. Great guidance as usual. It's a remote server so I have to use smtps. I'll get a cert and see if I can make it work!
That works great. I had to add the "smtpd_tls_CAfile" option to main.cf to get it working but it's perfect now. Thanks.
For a Let's Encrypt cert: https://www.howtoforge.com/community/threads/letsencrypt-on-mail-server.73695/
