The server is written assuming there's at least one valid SSL/TLS
certificate. For example, it unconditionally advertises STARTTLS, and
only supports AUTH over TLS.
This patch makes the server fail to listen if there are no certificates
configured, so the users don't accidentally run an unsupported
configuration.
glog works fine and has great features, but it does not play along well
with systemd or standard log rotators (as it does the rotation itself).
So this patch replaces glog with a new logging module "log", which by
default logs to stderr, in a systemd-friendly manner.
Logging to files or syslog is still supported.
It's more convenient and in line with standard practice to fail RCPT TO if the
user does not exist.
This involves making the server and client aware of aliases, but it doesn't
end up being very convoluted, and simplifies other code.
This patch adds checks that verify:
- The envelope from must match the authenticated user. This prevents
impersonation at the envelope level (while still allowing bounces, of
course).
- If the destination is remote, then the user must have completed
authentication. This prevents unauthorized relaying.
The patch ends up adjusting quite a few tests, as they were not written
considering these restrictions so they have to be changed accordingly.
