I believe some states have anti-spam laws that require a site to quit sending to a recipient when they are informed that the recipient has flagged the email as spam. I would guess that Y! is complying, but their emails just aren¡¯t flagged as spam as often.
?
As for why .io? Taste? I think the name is kind of cool myself¡
?
Re the incredimail fanfaron, I looked at the html of the sample. I¡¯m not a human html parser, but I¡¯ve done some work on XML standards. HTML parsing and interpretation is not as standardized as one could wish, and parsing in email tools is even more uneven. I pity Mark & Co for having to deal with it. My recommendation for an easy life is to avoid fancy stuff, but that¡¯s a matter of taste.