You can use transform sets in Relativity to pull the domains used in email fields. Transform sets use code to extract data from a source field and send it to a destination.
Follow these steps:
Assuming you have admin rights, click on the Transform Sets tab and select the handler Domain Parsing in the new set you create . . .
. . . create a field using the multiple object field type, and give it the 'Transform Set' associative object type.
Click 'Edit' on the transform set you have just created and select a source field contain email address, and also select the field you just created.
. . . click on 'Save' and then run the full transform set on the console panel.
The 'Domain Pull' field will be populated the copyee email domains.
If the production is augmented, you have the option of going back to the Transform Set and clicking on 'Start Transform: Incremental' , which will run it on any new documents.