Hah, even beyond the question of address format variations there are also commercial services that do some level of email address validation - and one of them r

Hah, even beyond the question of address format variations there are also commercial services that do some level of email address validation - and one of them regards my business email address as invalid (firstname@companyname.com) - adding another letter works, adding punctuation works, it's just my specific first name. Unfortunately it's done via black box on their server(s), so it's not like I can even dig through the code and figure out what's going wrong.