SMTP Error (530) 5.7.0 Must issue a STARTTLS command first

I am trying to use port 587 in roundcubemail running in the same machine as my mail server, and I am always receiving this error: SMTP Error (530): Failed to set sender "X" (5.7.0 Must issue a STARTTLS command first). I have already changed, smtpd_tls_security_level=encrypt to smtpd_tls_security_level=may and nothing happens, and I have already 'submission' uncommented. Those was the solutions that I have found to solve this problem, but till now no result here. Main.cf: http://pastebin.com/aEtC0AJt Master.cf: http://pastebin.com/023uu2T8 System specs: 1. PHP Version 5.6.25 2. Postfix 3. MacOS 10.12 I don't know if it is related, but I cannot login through IMAP port 993. I am only able to use ports 25 and 143 without SSL. I cannot send mails internally, all mails pass through my ISP mail server, where my email domain is.