Thanks, glad it worked for you! Sure, yeah you can extend it. Basically all it’s doing is searching for a specific string unique to the unwanted emails. It then sends any emails in which it finds the string to your spam folder with the “GmailApp.moveThreadToSpam(threads[i])” line.

If you want to have it search for multiple strings, like different domains for instance, you can add them in with OR operators in the “if(body.indexOf(“X-Forwarded-For: email@example1.com email@example2.com“)>-1)” line.

Alternatively, you could add additional “else if” statements underneath the above line. I’m no coding expert, so there may be a more efficient way to do it, but I hope that points you in the right direction.

Could you extend the script to support different headers, like a list of domains or IPs? (I tested it, it worked fine with one)

It’s possible it’s just not there. Are you sure it was sent via another domain? Try a Ctrl-F search for the domain it was sent via. Maybe it’s listed under a different header and you can use that instead. As long as you are copying and inserting a text string that is unique to the “via” spam then it should work just the same.