Hi , if your using I device and obviously you've set up an e mail / gmail adress with your password , here's the easiest solution .
Go to your settings menu
scroll down to mail ,contacts , calendar . ( tap on )
you should see your email address (tap on )
you should see your gmail acct. and at the bottom delete acct. (Tap on delete ) not to worry your acct is a fixed or an assigned acct only to you and will always remain .
Now you will be asked to add an account
Choose your provider ,Google , yahoo , hotmail ,etc
Follow the instructions and TYPE YOUR FIRST AND LAST NAME, ORIGINAL USED PASSWORD (APPLE ) , AND IF YOU WANT A DESCRIPTION FOR THIS ADDRESS ,ie : default adress , recovery adress , email 1 , email 2 . Etc etc .......then
you will see in upper right hand corner continue or done . Should be Done . Tap done.
You do not need to open SMTP or you do not need to add server . It is located through automatically.
Your done ! Should open email app icon and send or receive mail . If you get an error pop up then you've most likely entered wrong password . Use your apple password . Not your Google or other provider password