.io isn't a gTLD at all, it's a ccTLD belonging to British Indian Ocean Territory (which I find to be bullshit, since those islands have no permanent inhabitants).
That said, there are ccTLDs which behave more like gTLDs (like .io, .me, .fm, .gg, .cd) and are treated as such across much of what you do online, but whether that'll impact your email delivery depends on who you communicate with and how they treat spam.
That said, there are ccTLDs which behave more like gTLDs (like .io, .me, .fm, .gg, .cd) and are treated as such across much of what you do online, but whether that'll impact your email delivery depends on who you communicate with and how they treat spam.