@stefan do you have the IP address? You can do a reverse lookup

@stefan or use MxToolbox to check the quality if emails from the domain?

@stefan can you come up with a legitimate reason for a lot of Vietnamese people to sign up for a New Jersey themed social media site en masse?

@stefan .VN is the TLD for Vietnam, so I don't expect that people from around here would be signing up there unless they were looking for a disposable address. And I vaguely remember some article on cybersec that called out Vietnam as home to a bunch of big botnets.