My wife complained that her iPhone 6 can't send email on her Verizon Acct. Yet she receives emails fine.
I learned that when you create an email acct in iPhone 6 as type "Other" which is what you'd use to setup verizon.net
The iPhone 6 IOS does NOT properly format your SMTP settings: username and password
Instead of just properly entering a username of "user" it auto-enters "user@verizon.net" (which is wrong !) This will cause an error on iPhone saying username is wrong and you can't send email.
I also found that the password that you you initially entered on first setup screen becomes corrupt when your iPhone 6 enters it in the SMTP password field. This will cause the same error saying that you can't send email because your username/password is wrong.
Both these mean that you will not be able to send email messages because of this. Change both and things will work and you can send email
FWIW - This really isn't Verizon's fault - its an iPhone IOS defect ( or worse a virus of some kind )
Good Luck
BigDaddy__68