communications from eavesdroppers and attackers.
or more router that is not controlled or trusted by either entity.
alter the communications between the server and client.
agent it knows than from one it doesn't know.
security to many other common protocols that run over TCP.
server allows use of TLS. It takes no parameters.
domain name on the right hand side of an Internet mail address.
[RFC-2034], the status code to be returned SHOULD be 5.7.0.
STARTTLS command must be the last command in a group.
authentication and/or privacy was achieved.
SMTP QUIT command immediately after the TLS negotiation is complete.
refused due to lack of security").
domain name that the client thought it was connecting to.
first command after a successful TLS negotiation.
authenticated by the SMTP client when the client received it.
and is beyond the scope of this document.
will be at least as secure as no use of TLS.
it could result in delayed processing.
the STARTTLS command to provide an authorization identity.
[RFC-1869]  Klensin, J., Freed, N, Rose, M, Stefferud, E. and D.