Advanced Form Validation
Enable proceed/fail on the top level domain name EG .com .ca etc. rather than just full email address to include/exclude entire sets of domain names.
This way, you can include in the block list or reject
Thanks for the reply. I've just realised that my request wasn't particularly clear. I want to exclude emails from all domains except for those email addresses belonging to .com, .ca, .gov and a few more TLDs. I managed to create a PHP snippet that seems to have done the job.