Powermta Configuration Guide May 2026

<domain *> max-smtp-out 20 max-msg-rate 1000/h max-msg-per-connection 10 use-starttls yes </domain> <bounce-handler bounces@example.com> command /bin/cat >> /var/log/pmta/bounces.log </bounce-handler> Logging <acct-file /var/log/pmta/acct.csv> record job,vmta,domain,rcpts,status,dsn-status,time roll daily </acct-file> 16. Restart & Verify After config changes:

<source 0.0.0.0/0> auth-user myuser mypass require-auth yes </source> Better: restrict injection to localhost or a specific internal IP. Use domain stanzas to tune retries, timeouts, and throttling per recipient domain. powermta configuration guide

<domain *> max-msg-per-connection 20 max-rcpts-per-message 100 </domain> Use multiple virtual MTAs with increasing limits: Always test with low volume first, especially for

Per-domain rate limiting:

Assign VMTA in the injection source:

<source 127.0.0.1> return-path bounce@example.com </source> PowerMTA captures DSNs and can route bounces to a local script or mailbox. Always test with low volume first

pmta check config # Validate syntax pmta reload # Graceful reload pmta restart # Full restart tail -f /var/log/pmta/pmta.log PowerMTA is powerful but requires careful tuning. Start with conservative throttles, monitor bounce logs, adjust domain stanzas based on ISP feedback, and use virtual MTAs to separate traffic types. Always test with low volume first, especially for new IPs/domains.