[exim] Retry rules for specific errors: error after initial …

I just realised that there is no way to specify that a retry rule applies when
the remote host says "421 host.domain.example: Too many connections" or
similar (instead of the normal "220 host.domain.example ESMTP" greeting) upon
connection. I guess it falls under lost_connection today, but isn't it common
enough to warrant its own code, like connect_4xx or greet_4xx? I shouldn't be
too hard to implement either.

-- 
Magnus Holmgren        holmgren@???
                       (No Cc of list mail needed, thanks)