error-throttle reduces sending when ISP rejects (hard bounce), defer-throttle cuts rate on soft errors.
auth mechanism = sasl; sasl_server = /usr/lib/sasl2; powermta configuration guide top
<domain *> # Sign all outbound mail add-sign-header true </domain> </virtual-mta> sasl_server = /usr/lib/sasl2
<smtp-pattern 4xx> pattern ^4[0-9]2 initial-pts 60 max-pts 3600 </smtp-pattern> powermta configuration guide top