Q: If I respond to an email from my Iphone - it uses my icloud account rather than my gmail account - Is it safe to turn Icloud off in my mail settings if I never use it.  Thank you

I currently use my Iphone6 to respond to email.  I have a gmail account and that is the account I want to reply from, but the replies are always from Icloud.  Is it because I have Icloud open in my mail settings and is it ok to turn Icloud mail off.  Thank you