MX gateway and relay server integration for Sendmail environments

Pitbull integration with Sendmail

In environments using Sendmail, 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 routed through Pitbull relay via Sendmail mailertable and smart_host macro.

Relay Server Configuration

Sendmail relay is configured in /etc/mail/sendmail.mc with define(`SMART_HOST', `relay.pitbull.com.tr')dnl. Recompile with m4 sendmail.mc > sendmail.cf and restart the service. Use /etc/mail/mailertable for per-domain routing.

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 Sendmail:

# /etc/mail/sendmail.mc
define(`SMART_HOST', `relay.pitbull.com.tr')dnl
define(`RELAY_MAILER_ARGS', `TCP $h 587')dnl
FEATURE(`authinfo')dnl

# Compile and restart
m4 sendmail.mc > /etc/mail/sendmail.cf
systemctl restart sendmail

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.