channel keywords are used to configure SASL use, specifically the use
of the AUTH command, during the SMTP protocol by SMTP based channels
such as TCP/IP channels.
nosasl is the default, and means
that SASL authentication will not be permitted or attempted. It
nosaslserver, which means that SASL
authentication will not be permitted. Specifying
maysaslserver will cause the SMTP server to permit clients
to attempt to use SASL authentication. Specifying
mustsaslserver will cause the SMTP server to insist that
clients use SASL authentication; the SMTP server will not accept
messages unless the remote client successfully authenticates. The
saslswitchchannel keyword is used to cause incoming
connections to be switched to a specified channel upon a client's
successful SASL use. It takes a required value, specifying the channel
to which to switch.
nosaslswitchchannel is the default,
and means that channel switching is not performed upon a client's
successful SASL use.
See Section 14.4 for further discussion and examples of use of these channel keywords.