+TF/06 The fix for widen_domains has also been applied to qualify_single and
+ search_parents which are the other dnslookup options that can cause
+ header rewrites.
+
+PH/49 Michael Haardt's randomized retrying, but as a separate retry parameter
+ type ("H").
+
+PH/50 Make never_users, trusted_users, admin_groups, trusted_groups expandable.
+
+TF/07 Exim produced the error message "an SRV record indicated no SMTP
+ service" if it encountered an MX record with an empty target hostname.
+ The message is now "an MX or SRV record indicated no SMTP service".
+
+TF/08 Change PH/13 introduced the possibility that verify=helo may defer,
+ if the DNS of the sending site is misconfigured. This is quite a
+ common situation. This change restores the behaviour of treating a
+ helo verification defer as a failure.
+