+JH/12 Enforce a data synch check before emitting the 354 "go ahead". Previously
+ this was only done if a pre-data ACL was configured.
+
+JH/13 Refuse to accept a line "dot, LF" as end-of-DATA unless operating in
+ LF-only mode (as detected from the first header line). Previously we did
+ accept that in (normal) CRLF mode; this has been raised as a possible
+ attack scenario (under the name "smtp smuggling").
+