This topic will help set up a connector to use by a RULE if email meets the requirements like in this scenario:
Outbound mail is going through your hosting system but for some reason when an incoming mail is received from an external user i.e.: email@example.com and the recipient has a forward to an external account firstname.lastname@example.org , that email may be blocked with error explaining that relaying is denied, and the reason is that the server thinks that someone is trying to relay through as the forwarded email kept the external FROM address i.e.: email@example.com .
To fix this you will need to create a Connector that is sending from O365 directly to the outside with one condition which is if it is called by a RULE.
I- Creating a connector:
1- open the Exchange Admin Center (EAC)
2- Click on mail flow
3- Click on connectors (on the right pane)
4- click on the PLUS sign
In the connector Popup window:
5- in the From : chose "Office 365"
6- TO: chose "Partner Organization"
7- click NEXT
8-fill in the Name of the RULE
9- Add a description (this is very important if you have many connectors) then click NEXT
10- Chose "Only when i have a transport rule set up that redirects messages to this connector"
11-Chose " Use the MX record associated with the partner's domain" then NEXT
12- Leave the setting by default and click NEXT
13- A recap of your configuration will be displayed, then click NEXT
14-Add and External email address i.e.: firstname.lastname@example.org click Validate
Once the connector is created, we now need to create the RULE that calls this connector if the condition is met.
II- Creating a RULE:
Always in the EAC, click the RULES on the top left
1- Click on the(+) to create a new RULE
2- Enter a name for the RULE
3- Under "Apply this rule if..." chose "the sender is located..." then "Outside the organization" in the pop up window
4- Under "Apply this rule if..." chose "the recipient is located..." then "Outside the organization" in the pop up window
4- Uncheck "Audit this rule with severity"
5- click on "More option..."
6- Under "Do the following ..." chose "Redirect the message to" then chose "the following connector"
7-In the title pop up window chose the connector you just created in our example "Special outbound connector"
8- Make sure that your select the option "Stop processing more rules"
- Move the RULE to the top of the list