[Exim] message_size_limit buglet

Hi!

Setting message_size_limit to a ridiculous high value (for example
2048M) results in quite strange behaviour from the exim daemon (exim
4.22 on FreeBSD 4.8 with exiscan here) - it will immediatly drop the
TCP-connection on connect while logging "unable to expand
message_size_limit: NULL" to the paniclog.
While I definitly don't think it's a good idea to send messages this
large(this one was a configuration mistake) - exim should a least give
a reasonable warning in this case instead of silently failing :-)


Stefan