One of the guys confirmed with the email provider - poloniex never sent the outbound email to confirm disabling email verification when 2fa is active.
That confirms it, though it was already obvious that "smtp problems on the receivers end" was bs, since the registration confirmation email came fine, just some hours before.
Either they are deliberately withholding sending these emails (possibly to free email accounts only), or there is some sort of manual verification going on.
Whatever it is, it's not "smtp issues".