+ * If built with TLS support, then Exim will now validate the value of
+ the main section tls_require_ciphers option at start-up. Before, this
+ would cause a STARTTLS 4xx failure, now it causes a failure to start.
+ Running with a broken configuration which causes failures that may only
+ be left in the logs has been traded off for something more visible. This
+ change makes an existing problem more prominent, but we do not believe
+ anyone would deliberately be running with an invalid tls_require_ciphers
+ option.
+
+ This also means that library linkage issues caused by conflicts of some
+ kind might take out the main daemon, not just the delivery or receiving
+ process. Conceivably some folks might prefer to continue delivering
+ mail plaintext when their binary is broken in this way, if there is a
+ server that is a candidate to receive such mails that does not advertise
+ STARTTLS. Note that Exim is typically a setuid root binary and given
+ broken linkage problems that cause segfaults, we feel it is safer to
+ fail completely. (The check is not done as root, to ensure that problems
+ here are not made worse by the check).
+
+ * The "tls_dhparam" option has been updated, so that it can now specify a
+ path or an identifier for a standard DH prime from one of a few RFCs.
+ The default for OpenSSL is no longer to not use DH but instead to use
+ one of these standard primes. The default for GnuTLS is no longer to use
+ a file in the spool directory, but to use that same standard prime.
+ The option is now used by GnuTLS too. If it points to a path, then
+ GnuTLS will use that path, instead of a file in the spool directory;
+ GnuTLS will attempt to create it if it does not exist.
+
+ To preserve the previous behaviour of generating files in the spool
+ directory, set "tls_dhparam = historic". Since prior releases of Exim
+ ignored tls_dhparam when using GnuTLS, this can safely be done before
+ the upgrade.
+
+