Open-Xchange
Mail server variant for Open-Xchange, OX App Suite and OX Mail. Smart host and mailfilter Sieve rules.
Prerequisite: Step 1, Domain & DNS Setup is complete and all four DNS checks are green.
What happens here: The OX MTA, the Postfix stack under Open-Xchange, is configured to use Conbool as its smart host. Inbound connections from Conbool are allowed. Loop protection and spam classification run via
mailfilterSieve rules. In the Setup Assistant, the Manual configuration mode is chosen.Effort: 30 to 60 minutes.
Step A. Outbound Smart Host in OX
Navigation: OX server administration → Mail server configuration, or directly in the Postfix configuration.
| Field | Value |
|---|---|
| Smart host or relay host | mail.conbool.com |
| Port | 25 |
| Authentication | None, identification via TLS certificate and sender domain |
| TLS | Required |
| TLS certificate name | mail.conbool.com |
| MX lookup for smart host | Disabled |
| Scope | All hosted domains, optionally specific domains of the OX installation |
Step B. Allow Inbound Connections from Conbool
So that Conbool may deliver mail to OX, the Conbool IP addresses are added as a trusted relay source.
- Receiving MTA: Make port
25for SMTP reachable from the Conbool IP addresses. Conbool provides the IP list. - Recipient whitelist: Accept only the domains hosted in OX, i.e. standard recipient restrictions.
- TLS: Require for inbound connections from Conbool.
- Certificate validation: Allow TLS certificate name
mail.conbool.com.
Firewall: Port 25 (SMTP) must be open from the Conbool IP addresses to the OX MTA. If running behind a load balancer, maintain the whitelist there as well.
Step C. Loop Protection and Spam in mailfilter Sieve Rules
OX has no central transport rule engine like Exchange. The logic is implemented via mailfilter Sieve rules per tenant or global, or via Postfix header checks.
- Loop protection. Messages with
X-Conbool-<YourDomain>: true(e.g.X-Conbool-example-com: true) must not be sent through Conbool again. Deliver directly via the regular MX. - Spam classification. Messages with
X-Conbool-Flag: YESgo to the Spam folder. Sieve actionfileinto "Spam"or markerX-Spam-Flag: YES. - Calendaring and empty Return-Path. Calendaring messages and
Return-Path: <>are excluded from smart-host routing.
If an OX-internal connector module or a third-party mail-routing plugin is used, apply the conditions above as exceptions in its rule set.
Done When
Back in the Setup Assistant at the Mail Server step. Enter the relay host of the OX inbound MTA, for example mx-internal.yourcompany.com, then click Test Connection. Status "SMTP reachable" means the connection is established.
Continue with the connection test and completion.