JavaScript form validation with else if

I have been creating JavaScript validation for a form though run into difficulties. There are currently two parts to parts at (at the moment) for JavaSCript to check (email and sms). THe script is only running email and not checking sms at all when should be checking both together. If both are fine then return true. Any ideas?

function validateForm() {
    var emailBoxChecked = document.getElementById("checkemail").checked
    var emailBoxChecked = document.getElementById("checksms").checked
    var errordiv = document.getElementById('error');
    var errorsms = document.getElementById('errorsms');
        /*postOptOutSix.checked = false;
        postOptOutForever.checked = false*/
    // Conditions
    if (document.getElementById("emailradios") ==null && document.getElementById("emailforever") ==null) {
        if (document.getElementById("smsforever") ==null && document.getElementById("smsforever") ==null) {
            return true;
        }
        else if (document.getElementById("checksms").checked ==false && document.getElementById("smsOptOutSix").checked ==false && document.getElementById("smsOptOutForever").checked ==false) {  
            errordiv.innerHTML += "<p id='errorp' style='color:red;'>*SMS - Please either opt-in post or select either of the options.'";
            return false;
        } else {
            return true;
        }
    }
    else if (document.getElementById("checkemail").checked ==false && document.getElementById("emailOptOutSix").checked ==false && document.getElementById("emailOptOutForever").checked ==false) {  
        errorsms.innerHTML += "<p id='errorp' style='color:red;'>*Email - Please either opt-in post or select either of the options.'";
        return false;
    } else {
        return true;
    }
}