PowerMTA (PMTA) is not a standard MTA. It's a mail transfer agent optimized for outbound throughput, queue management, and sender reputation. Unlike Postfix or Exim, PMTA is event-driven, asynchronous, and designed to handle millions of connections per hour.
This guide assumes you have a valid license and have installed PMTA (typically in /etc/pmta/). The main configuration file is config (or config.dat post-compile). powermta configuration guide top
# Validate syntax
/usr/sbin/pmta configtest
6. dns-timeout (Resolver Speed)
Slow DNS kills throughput.
dns-timeout 10s
dns-retries 2
9. Common Pitfalls & Fixes
| Problem | Likely Cause | Solution |
|---------|--------------|----------|
| 450 4.7.1 Service unavailable | You hit ISP rate limit | Lower max-msg-rate for that domain |
| Emails queued, not sending | No reverse DNS for your source IP | Configure rDNS with your ISP |
| DKIM fails | Wrong selector or private key path | Test with pmta test-dkim --domain example.com |
| High deferrals | No SPF on sending domain | Add v=spf1 ip4:YOUR_IP ~all to DNS | PowerMTA Configuration Guide: From Core to Edge (Deep
9. Secure PowerMTA
To secure PowerMTA, you can:
- Use TLS encryption for secure email delivery.
- Configure authentication using SASL or external scripts.
- Limit access to the PowerMTA server using firewall rules.
Example:
iptables -A INPUT -p tcp --dport 25 -j ACCEPT
iptables -A INPUT -p tcp --dport 587 -j ACCEPT