[exim] Rate Limit

# Slow down fast senders; note the need to truncate $sender_rate

# at the decimal point.
warn ratelimit = 100 / 1h / per_rcpt / strict
     delay     = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
                   $sender_rate_limit }s

Anyway to make this NOT limit authenticated senders?