Scenario:
There are times when clients create a distribution where a number of emails address reside outside of the O365 tenant or simply wanting to forward a single email to an outside mailbox from O365.
Solution:
What is required in Exchange Online is creating a rule that is only associated with a send connector which will resolve the destination domain via MX records.
1- Create Send Connector.
2- Create Rule which is Associated with the Connector.
1- Login to https://admin.exchange.microsoft.com and click on MAIL FLOW then CONNECTORS and click on ADD A CONNECTOR.
2- Create a connector with the following conditions and click CREATE CONNECTOR then DONE.
3- Click on RULES and click ADD RULE and select CREATE NEW RULE.
4- Create a rule with the following conditions and click FINISH then click DONE.
5- Enable the rule as by default it is created disabled.