Associating email captured cases with the correct customer record

Hey,

I'm setting up NetSuite to capture the support cases for our software and I'm trying to figure out the best way to do it. Email case capture is good, but the issue arises when someone emails a case from an address we don't already have.

Is there some way to filter based on the domain the email was sent from rather than the whole address? Alternatively/Additionally, is there some way to parse the email and use the company name to associate the records?

Thanks,
Erik