Automatically send email about editing google spreadsheet - email

Question

I'm working on a rather simple script which should handle new values in the spreadsheet and then send emails to specified addresses. And I faced with the problem. My code is listed below:
function onEdit(e) {
//part of the code for checking e.range to process only updated values
sendEmail();
}
function sendEmail() {
// arguments are missed only for demo
GmailApp.sendEmail();
}
While I'm using "simple trigger", my function "sendEmail()" works only if I start it from script editor. I allowed sending emails on behalf of my at first time and then function works fine. But if I'm changing the value in the spreadsheet - function "onEdit(e)" processes new data but function "sendEmail()" does nothing.
I partly solved this problem by using project's triggers from "current project's triggers" menu. In that case, function "sendEmail()" works properly, but I have no access to the information about update.
For my purposes I could use just second way and find new values "manually" every time, but I wish to optimize this work.
So, my questions are:
Is the process I described above proper or I made a mistake
anywhere?
If process proper, is where a way to combine both cases?
Thanks!

Answer 1

You correctly understood that (as the docs say) simple triggers cannot send an email, because they run without authorization. An installable trigger, created via Resources menu, can: it has the same rights as the user who created the trigger. If it is set to fire on edit, it will get the same type of event object as a simple trigger does.
So, a minimal example would be like this, set to run "on edit":
function sendMail(e) {
MailApp.sendEmail('user#gmail.com', 'sheet edited', JSON.stringify(e));
}
It emails the whole event object in JSON format.
Aside: if your script only needs to send email but not read it, use MailApp instead of GmailApp to keep the scope of permissions more narrow.