NodeJS Q Promise erroring "has no method 'then'" - node.js

Question

I'm working on implementing a promise (first time using them with node) but I keep getting the error:
TypeError: Object function (){
Users.findById(req.body.receiver).exec(function (err, user){
if(err) return handleError(err);
if(user.local.email ){
return email = user.local.email
}
if(user.facebook.email){
return email = user.facebook.email
}
})
} has no method 'then'
Judging by the error I'm going to have to guess there is something wrong with return function()?
Here is my function:
exports.sendEmail = function(req,res){
function findEmail(){
return function(){
Users.findById(req.body.receiver).exec(function (err, user){
if(err) return handleError(err);
if(user.local.email ){
return email = user.local.email
}
if(user.facebook.email){
return email = user.facebook.email
}
})
}
}
findEmail().then(function(email){
// do stuff
})
}

Answer 1

function findEmail(){
return function(){
return Q();
};
}
findEmail(); // returns a function
In your example the findEmail returns a function that if called returns a promise. However your attempting to use the returned function as if it was a promise which it isn't it's a function.
Two ways to fix:
findEmail()(); // returns the promise
Or refactor the function:
function findEmail() {
return Q();
}
findEmail(); // returns the promise
Notice the missing return function()?

Answer 2

Too much nesting? Do you really need that extra function wrapper?
exports.sendEmail = function(req,res){
function findEmail(){
Users.findById(req.body.receiver).exec(function (err, user){
if(err) return handleError(err);
if(user.local.email ){
return email = user.local.email
}
if(user.facebook.email){
return email = user.facebook.email
}
})
}
findEmail().then(function(email){
// do stuff
})
}
EDIT: I would also do some serious refactoring here, promisify stuff (mixing callbacks and promises is just not great visually, promisified code looks a lot better), avoid a named function if it's only used internally and once, etc...