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MX gateway and relay server integration for Microsoft 365 environments

Pitbull MX gateway for Microsoft 365 (Cloud, SaaS) mail servers: inbound filtering, quarantine and outbound relay. In Microsoft 365 environments MX records point to Pitbull gateway; hybrid setups use connectors for outbound relay.

Microsoft 365 · Relay MX + Relay Server
Inbound MX ROUTED
Relay AKTİF
Filter RSPAMD
Abuse OBSERVE
Microsoft 365 Relay MX Gateway Rspamd NOC
SaaS
Platform
Cloud
License
MX+Relay
Gateway model
KVKK
Local processing

Integration challenges

Pitbull solves mail security on this platform with the MX gateway model.

Limited native filtering

Microsoft 365 default spam protection is insufficient against advanced phishing and BEC attacks.

Outbound blind spot

Without relay configuration, outbound spam and abuse detection is delayed; IP reputation drops.

Missing central visibility

Hard to monitor traffic, quarantine and reject reasons from one point.

Scattered policy

Managing SPF/DKIM/DMARC and quarantine policies per server increases error risk.

Pitbull integration with Microsoft 365

In environments using Microsoft 365, 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: In Microsoft 365 environments MX records point to Pitbull gateway; hybrid setups use connectors for outbound relay.

Relay Server Configuration

Create a Pitbull relay connector under Mail flow → Connectors in Exchange Online Admin Center. Point MX records to the Pitbull gateway address.

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 Microsoft 365:

Exchange Admin Center → Mail flow → Connectors
  From: Your organization's email server
  To: Partner organization
  Smart host: relay.pitbull.com.tr
  Port: 587
  Authentication: TLS + Basic Auth

DNS MX:
  @  MX  10  mx.pitbull.com.tr.

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.

Smarthost configuration

Outbound relay and MX routing steps

Inbound — MX (gateway in front of Microsoft 365)

Deploy Pitbull as an additional security layer in front of Microsoft 365:

  1. Microsoft 365 Admin → Domains → DNS records
  2. Note existing MX (e.g. domain-com.mail.protection.outlook.com)
  3. Set primary MX to Pitbull: mx.pitbull.com.tr (priority 10)
  4. Configure M365 MX as delivery target in Pitbull panel

Outbound — Connector / Smarthost

For hybrid or on-prem relay scenarios via Exchange / M365 connector:

  1. Exchange Admin → Mail flow → Connectors
  2. New connector: From: Your organization's email server → To: Partner organization
  3. Smart host: relay.pitbull.com.tr, port 587
  4. Use Pitbull SMTP AUTH credentials

Alternative: On-prem Exchange Send connectors with smart host [relay.pitbull.com.tr]:587.

Ensure SPF includes both Microsoft and Pitbull sending IPs.

Illustrated setup guide

Pitbull integration on this platform is completed in 4 visual steps.

Gateway flow diagram
MX Gateway
1

MX Gateway

Point DNS MX to the Pitbull gateway address.

SPF · DKIM · DMARC
2

SPF · DKIM · DMARC

Add authentication DNS records.

Outbound Relay
3

Outbound Relay

Set Pitbull relay as smarthost / relayhost.

NOC Verification
4

NOC Verification

Send a test email and verify in the NOC panel.

Setup steps

  1. 1 Point DNS MX records to the Pitbull gateway address (priority 10).
  2. 2 Add Pitbull include to SPF; generate DKIM TXT from panel and add to DNS.
  3. 3 Set the Pitbull relay address in Microsoft 365 relay/smarthost settings.
  4. 4 Send a test email and verify inbound/outbound traffic in the NOC panel.
  5. 5 Start DMARC at p=none and monitor aggregate reports.
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