host to which Exim is connected supports TLS encryption.
.new
-.vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>
+.vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
.oindex "&%-MCt%&"
This option is not intended for use by external callers. It is used internally
by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
connection is being proxied by a parent process for handling TLS encryption.
-The pair of arguments give the local address and port being proxied.
+The arguments give the local address and port being proxied, and the TLS cipher.
.wen
.vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
hexadecimal digits. There may be fewer than eight components if an empty
component (adjacent colons) is present. Only one empty component is permitted.
-&*Note*&: The checks are just on the form of the address; actual numerical
-values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
-check. The main use of these tests is to distinguish between IP addresses and
+.new
+&*Note*&: The checks used to be just on the form of the address; actual numerical
+values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
+check.
+This is no longer the case.
+.wen
+
+The main use of these tests is to distinguish between IP addresses and
host names, or between IPv4 and IPv6 addresses. For example, you could use
.code
${if isip4{$sender_host_address}...
lines for the second and subsequent messages.
.new
When two or more messages are delivered down a single TLS connection, the
-TLS-related information logged for the first message delivered
-(which may not be the earliest line in the log)
+DNS and some TLS-related information logged for the first message delivered
will not be present in the log lines for the second and subsequent messages.
+TLS cipher information is still available.
.wen
.cindex "delivery" "cutthrough; logging"