Remote Domains

Configure remote domain settings to control how Exchange Online communicates with external domains. Remote domains define message format, out-of-office responses, and automatic forwarding behavior for messages sent to specific external domains.

Note: The default remote domain (*) applies to all external domains not explicitly configured. Custom remote domains override the default for specific domains.

Remote Domain List

Default Remote Domain

The default remote domain (*) applies to all external communication:

• Controls message format for all external recipients
• Defines out-of-office response behavior
• Manages automatic forwarding permissions
• Applies unless overridden by a custom remote domain

Message Format Options

Content Types

• Use Exchange rich-text format — Preserve TNF formatting (Outlook to Outlook)
• Never use Exchange rich-text format — Convert to HTML or plain text
• Allow MIME and plain text — Let Exchange determine best format

Character Sets

• Configure MIME and non-MIME character sets
• UTF-8 recommended for international communication
• Override for domains requiring specific character encoding

Out-of-Office Responses

Control how automatic replies are sent to the remote domain:

• External — Send external OOF messages only
• ExternalLegacy — Send both external and internal OOF messages
• InternalLegacy — Send internal OOF messages to external domain
• None — Do not send any OOF responses to this domain

Automatic Forwarding

Control whether messages can be auto-forwarded to the remote domain:

• Allow — Permit automatic forwarding to this domain
• Block — Prevent auto-forwarding to this domain
• Works in conjunction with outbound spam policy forwarding controls

Creating Custom Remote Domain

1. Specify domain — Enter the external domain name.
2. Message format — Set preferred content type and character set.
3. Out-of-office — Configure which OOF responses are sent.
4. Automatic replies — Enable or disable delivery reports and NDRs.
5. Forwarding — Allow or block auto-forwarding to this domain.

Common Scenarios

Partner Domain

Allow full communication features with a trusted partner:

• Enable out-of-office responses
• Allow auto-forwarding
• Use rich-text format for Outlook compatibility

Restricted Domain

Limit communication features with an untrusted domain:

• Disable out-of-office responses
• Block auto-forwarding
• Convert to plain text format

Best Practices

• Review default settings — Ensure the default remote domain matches your organization’s communication policy.
• Block forwarding by default — Disable auto-forwarding in the default remote domain.
• Configure partner domains — Create custom remote domains for trusted partners with appropriate settings.
• Test format changes — Verify message formatting after changing content type settings.

API Reference

GET /api/exchange/remote-domains List remote domains

POST /api/exchange/remote-domains Create custom remote domain

PUT /api/exchange/remote-domains/:id Update remote domain settings

DELETE /api/exchange/remote-domains/:id Delete custom remote domain