smtpd-starttls-proxy
Software
skarnet.org
The qmail-remote-io internal program
qmail-remote-io is a part of the SMTP client implemented by qmail-remote. It manages the entirety of the SMTP transaction except EHLO and STARTTLS.
qmail-remote-io is not meant to be invoked directly. It is meant to be executed into by qmail-remote.
Internal details
- qmail-remote does the job of finding a suitable SMTP server and connecting to it, saying EHLO and, if the user has defined a control/trustanchors file and the server supports it, STARTTLS.
- If the connection is not encrypted, qmail-remote execs qmail-remote-io immediately, and qmail-remote-io proceeds with all the rest of the SMTP transaction.
- If the connection is encrypted, qmail-remote execs s6-tlsc qmail-remote-io, instead, so any further exchange with the SMTP server is protected by TLS.
- qmail-remote-io does the same job in either case: it speaks plaintext SMTP.