Yes, that IS a real APS domain. They used it for VLNX, when they were briefly with Implix. Since then, they've used RedCappi, who evidently have their own email distribution system that doesn't require the client to create a specific domain.
But now there're problems with RedCappi. None of their https pages work.
Maybe they can't send email, either; I haven't heard from the real APS since Wednesday.
I think the email was spoofed.