+JH/21 Bug 3059: Fix crash in smtp transport. When running for a message for
+ which all recipients had been handled (itself an issue) a null-pointer
+ deref was done on trying to write a retry record. Fix that by counting
+ the outstanding recipients before trying to transmit the message.
+ The situation arose for a second MX try within a transport run, when the
+ first had perm-rejected a recipient (the only one for the connection, in
+ the case seen) during pipelining, and then closed the TCP connection.
+ The transport classified that as an I/O error, leaving the message
+ outstanding but having marked up the recipient as dealt-with. It then
+ tried another MX because of the I/O error. Fix this by converting the
+ message-level status to ok if there was a close but all recipients were
+ dealt with. Thanks to Wolfgand Breyha for debug runs.
+
+JH/22 The ESMTP_LIMITS facility (RFC 9422) is promoted from experimental status
+ and is now controlled by the build-time option DISABLE_ESMTP_LIMITS..
+