scroll through a list of known email providers and you will notice they registered tlds for the countries they operate in, very typical for the old ones like ya

scroll through a list of known email providers and you will notice they registered tlds for the countries they operate in, very typical for the old ones like yahoo yandex Freemail Hotmail etcpp web.de is an oldschool German provider, as is gmx.de (and .at, .fr, .com, ...) the regex smells like an inexperienced developer trying to be clever