Making sure it sends emails from your business email not my personal

I just responded to a client through email, and it opened up Apple Mail and sent them an email from my personal email that I created when I was a kid. I am a little bit embarrassed about it, needless to say. It is my fault for not double-checking, but I haven't even signed into my business email on my phone yet, and I was not expecting that at all. I was expecting that, since I put my business email under the Business settings tab, I just thought it would send that way. There just has to be an easier route or something for that.