SSL/TLS vs STARTTLS This seemed to be confusing at first but here is what it boils down to: With STARTTLS, an existing TCP connection is upgraded to an encrypted one after the SMTP handshake. On the other hand, with SSL/TLS, an ecnrypted connection is negiotiated right away before an SMTP handshake takes place. In other words, STARTTLS is "TLS inside SMTP", while SSL/TLS is "SMTP inside TLS". See this page for more information. Another important difference between these two schemes is that STARTTLS does not require a separate port. You can continue to use the same smtp (25) or imap (143) port. SSL/TLS on the other hand requires separate smtp (465) and imap (993) ports. Setup I wanted to implement a STARTTLS scheme; however, I decided to revert back to SSL/TLS due to: 1. I am running Dovecot dovecot-1.0.7 on CentOS release 5.5. Unfortunately for me, I was not able to require SSL connections since the "ssl = required" configuration option is not av...