For Office 365 Dedicated/ITAR customers, an outgoing connector should be configured by using the following settings:
|Outgoing connector configuration|
Description: Responsible for routing mail to Exchange Online Dedicated for customer's target address and primary SMTP domains
Connector type: On-premises
Retain service headers on transmission: <checked>
Connection security: Recipient certificate matches <customer fqdn\certificate SAN>
Outgoing delivery: Route mail through smart hosts
<Customer's dedicated smart host> (example: 999-1-mx.outlook.com)
"nnn" is the customer's 3 digit number
"r" is the region code. If there's a single region, use the region code 1. If there's multiple regions and if customer requires mail to route in a region only, customer may use the region code 2.
Route all accepted domains through this connector <checked>
This option makes sure that any domain that's associated with the tenant uses this connector unless that domain is explicitly added to an outgoing connector through the recipient domains list.
Customer can manage a select list of domains that they expect to flow to Exchange Online Dedicated in the recipient domains list. If the customer adds a new domain that they try to route to Exchange Online Dedicated, and if they manage this recipient domains list for the "From_EOP_to O365D" connector, they must update the recipient domains list to include the new domain, as in the following example: