Is there anyway to run a bulk search in my instance looking to match one column (email address) from a csv? I get some long files that need mass checks for compliance reasons (400 rows - match on one column) I can't find built solutions like workbench or app that do this. Thank you.
There is no built-in solution to consume a CSV and run a search against multiple objects for each row. You will need to build this using custom code, either on-platform or ideally in a middleware/ETL platform.
The code needed is not particularly complex, but you should be cognizant of the fine details of how SOSL builds a result set if you choose to use SOSL, as it may not return all potential matches to you.
If this is a one-off need, I would script it using your scripting language of choice (Python is mine) off-platform. If this is a recurring need, detailed analysis of your specific requirements and the tools available to you would be needed to settle on an architecture.