I don't think spamming and email addresses are in anyway correlated at all. If spamming made me a lot of money, I'd just register a domain like 12345immaspamyou

I don't think spamming and email addresses are in anyway correlated at all. If spamming made me a lot of money, I'd just register a domain like 12345immaspamyou12345.com and make as many email addresses as I want anyway. Rejecting legitimated email addresses in the name of security is the sort of dick move you'd expect from a bank.