why can i receive emails, but i can not send them on my S4?

[LB certified]

I keep getting send failed whenever I try to send an email from my gmail account off of my phone. This only began happening about a month ago. I don't mess with any settings, but one of my kids could've button smashed his/her way into this situation. Can someone help walk me though maybe resetting my settings to get this resolved?

 

[B. Diddy]

Welcome to Android Central! Are you using the stock Email app, or the actual Gmail app?