MX gateway and relay server integration for OpenSMTPD environments

Pitbull integration with OpenSMTPD

In environments using OpenSMTPD, Pitbull integration works on two channels:

• Inbound: DNS MX records point to the Pitbull gateway; Rspamd-based filtering, quarantine and policy engine secure inbound traffic.
• Outbound: Outbound traffic is directed to the Pitbull relay via OpenSMTPD smtpd.conf action relay via.

Relay Server Configuration

OpenSMTPD relay is configured in /etc/smtpd.conf with action "relay_pitbull" relay via smtp+tls://relay.pitbull.com.tr auth <secrets>. Use a match rule to direct outbound traffic to this action.

Inbound MX Gateway

• Point domain MX records to the Pitbull gateway address (priority 10)
• Rspamd spam, phishing and malware filtering at the gateway layer
• Malicious attachment scanning via ClamAV / Avast REST
• SPF, DKIM and DMARC checks + score breakdown
• Suspicious messages isolated in quarantine; admin-approved release workflow

Outbound Relay Settings

To route outbound traffic to the Pitbull relay on OpenSMTPD:

# /etc/smtpd.conf
table secrets file:/etc/mail/secrets

action "relay_pitbull" relay via smtp+tls://label@relay.pitbull.com.tr:587 auth <secrets>

match from local for any action "relay_pitbull"
match from src 192.168.0.0/16 for any action "relay_pitbull"

This configuration passes outbound traffic through the Pitbull outbound filtering engine. SMTP Abuse Radar, per-tenant rate limits and Emergency Outbound Lockdown are activated.

Authentication

• Add Pitbull include to SPF
• Enable DKIM signing from Pitbull panel and publish DNS TXT record
• Start DMARC at p=none and monitor reports

Operational Visibility

Monitor delivery rates, reject reasons, queue status and GeoIP/ASN distribution on NOC screens. Deliver periodic security summaries to management teams with executive PDF reports.