Sent email appearing in inbox iPhone

If a recipient doesn't answer my question in a few days, Apple puts the email I sent in my inbox. I don't want this. I know who has answered and who has not. I do not see where or how to turn off this extremely annoying, intrusive feature. It only happens on my iPhone, not on my mini. It is not every email, only the ones with questions that have not been replied to. No, I have not asked to bcc myself.