To successfully configure your mail server, connectors, transport rules, and a correct MX record are required.
The following describes the setup with Microsoft Exchange Online. The procedure can be applied analogously to other mail servers.

Overview

1. Set Up Connectors

Connectors control the mail flow between your Microsoft 365 organization and Conbool. Two connectors are required:

Inbound
From Conbool → Your organization

Outbound
From your organization → Conbool

Navigation: Microsoft 365 Admin Center → Exchange Admin Center → Mail flow → Connectors

Inbound Connector (From Conbool)

Allows Conbool to deliver emails to your organization.

1. Click + Add a connector.
2. Connection from: Partner organization
3. Connection to: Office 365
4. Name: From Conbool
5. Authentication / Identifying the partner organization:
   • Recommended: By verifying that the subject name of the certificate matches this domain name → mail.conbool.com
   • Enforce TLS: Enable Reject emails if they are not sent over TLS
6. Review summary → Create connector.

Alternative (not preferred): Authentication via IP list. Certificate verification via mail.conbool.com is more update-proof in case IPs change.

Outbound Connector (To Conbool)

Routes emails from your organization through Conbool.

1. Click + Add a connector again.
2. Connection from: Office 365
3. Connection to: Partner organization
4. Name: To Conbool
5. Usage: Only when email messages are routed through these smart hosts
   • Smart host: mail.conbool.com
6. Security settings:
   • Enable Always use Transport Layer Security (TLS)
   • When connecting with: Certificate issued by a trusted certificate authority
   • Optional (recommended): Certificate name must contain mail.conbool.com
7. Validation email: Enter an external address and start validation.
   • Note: Validation may fail if the transport rule (e.g., X-Conbool header) is not yet active. In practice, this is usually not critical.
8. Review summary → Create connector.

2. Define Transport Rules

Transport rules control which messages are routed through Conbool and prevent loops.

Navigation: Exchange Admin Center → Mail flow → Rules

Rule "Relay to Conbool"

Determines which emails are routed through Conbool.

1. Create new rule → + New rule.
2. Name: Relay to Conbool.
3. Apply this rule if…
   • e.g., The sender is located… → Inside the organization (adjust as needed)
4. Do the following…
   • Redirect the message to the following connector → To Conbool
5. Except if… (prevent loops)
   • The message headers match these text patterns
   • Header name: X-Conbool-<YourSecondLevelDomain-TopLevelDomain> (e.g., X-Conbool-example-com)
   • Value: yes
6. Review settings → Save and Enable.

(Optional) Rule "Classify Spam"

Automatically classifies emails marked as spam by Conbool.

1. Create new rule → + New rule.
2. Name: Classify Spam.
3. Apply this rule if…
   • Message header contains → X-Conbool-Flag = YES
4. Do the following…
   • Set SCL to 7 (message is moved to the Junk folder)
5. Review priority/mode → Save and Enable.