[exim] proxy protocol and smtp_reserve_hosts etc.pp.

I run an outbound gateway (4 nodes) behind a F5 which shall (sic) be
relocated into a diffrent network and the new LB can't preserve the senders
IP but can do proxy protocol...

Currently I do use smtp_accept_reserve / smtp_reserve_hosts to ensure
the top sending ips get a free slot and helo_accept_junk_hosts for a few
IPs ...

I guess those must be reworked as well as black-listing per IP in
acl_check_connect and rate-limiting in acl_check_rcpt?

Thanks for any hints,
urs