I understand that email from external was rejected to email group [email protected].

 

It seems that the group posting permission configuration was incorrect.

 

Please kindly update the configuration to "public".

 

  1. Open Google Groups.
  2. Click My Groups > name of the group you want to edit.
  3. Click Manage in the upper-right corner.
  4. From the left-hand navigation menu, click Permissions > Basic Permission > Post > Public.
  5. Make your changes and click Save in the upper-left corner.